Betelgeuse. Before, During and After the Great Dimming

When a prominent star in the night sky suddenly dims, it generates a lot of interest. That’s what happened with the red supergiant star Betelgeuse between November 2019 and May 2020. Betelgeuse will eventually explode as a supernova. Was the dimming a signal that the explosion was imminent?

No, and new research helps explain why.

Headline writers couldn’t resist the supernova angle, even though that explanation was never very likely. Eventually, it became clear that ejected dust from the star caused the dimming. New research based on observations before, during, and after the Great Dimming Event (GDE) supports the idea that dust from the star itself caused Betelgeuse’s drop in brightness.

A research letter titled “Images of Betelgeuse with VLTI/MATISSE across the Great Dimming” presents the infrared observations of Betelgeuse. The observations capture the star before, during, and after the GDE. The lead author is Julien Drevon, from the Université Côte d’Azur, France, and the European Southern University.

“To better understand the dimming event, we used mid-infrared long-baseline spectro-interferometric measurements of Betelgeuse taken with the VLTI/MATISSE instrument before (Dec. 2018), during (Feb. 2020) and after (Dec. 2020) the GDE,” the research letter states. In particular, their observations focus on silicon monoxide (SiO.)

The authors of the new research outline three steps in the process that created the GDE.

Step One

The GDE started with shocks deep inside Betelgeuse. They generated a convective outflow of plasma that brought material to the star’s surface. Researchers detected a strong shock in February 2018 and a weaker one in January 2019. The second, weaker shock boosted the effect of the stronger shock that preceded it, generating a progressive plasma flow at the surface of Betelgeuse’s photosphere.

Step Two

The plasma flowing to the photosphere’s surface created a hot spot. Hubble UV observations of Betelgeuse revealed the presence of a luminous, hot, dense structure in the star’s southern hemisphere, between the photosphere and the chromosphere.

Step Three

Stellar material detaches from the photosphere and forms a gas cloud above Betelgeuse’s surface. A colder region forms under this cloud as a dark spot. Since it’s cooler, dust is allowed to condense above this region and in the part of the cloud above it. That dust is what blocked some of Betelgeuse’s luminosity, causing the GDE.

Previous research revealed this three-step process behind the GDE. The authors of the new research article set out to observe Betelgeuse’s close circumstellar environment to probe and monitor its geometry. In the wavelength range they worked in, SiO spectral features are prominent, and they’re used to understand what happened with the red supergiant. In astronomy, SiO is used as a tracer for shocked gas in stellar outflows since it persists at high temperatures.

This figure from the research letter shows some of the data the researchers worked with. The top panel shows the absolute spectra during each observed epoch. The bottom panel shows the relative flux for the SiO bands. The bands are deeper during the GDE than either before or after. Image Credit: J. Drevon et al. 2024.

In their article, the authors focus on the SiO (2-0) band and what it signifies. They note how the band’s intensity contrast increases by 14% during the GDE. “Therefore, it seems that during the GDE, we observe brighter structures in the line of sight,” they explain.

Next, they note a 50% decrease in intensity contrast in December 2020. What does it mean?

“The SiO (2–0) opacity depth map shows, therefore, strong temporal variations within 2 years, indicative of vigorous changes in the star’s environment in this time span,” they write.

Their observations also suggest “the presence of an infrared excess in the pseudo continuum during the GDE, which has been interpreted as new hot dust formed,” Drevon and his colleagues write.

This figure from the research article explains some of what the researchers found. The middle column is particularly interesting because it’s a reconstruction of the SiO (2-0) absorption band onto Betelgeuse’s surface for each of the three observed epochs. The third column is similar but shows the SiO (2-0) optical depth. Overall, they constrain the geometry of the dust feature that caused the GDE. Image Credit: J. Drevon et al. 2024.

It seems like the Great Dimming is no longer the mystery it once was. It also shows that Occam’s Razor is alive and well: “The explanation that requires the fewest assumptions is usually correct.”

The supernova proposal was fun for a while, and one day, Betelgeuse will explode as a supernova. But before it ever does, there are likely going to be several more episodes of dimming. For now, the authors say that the star is returning to normal.

“The Dec. 2020 observations suggest that Betelgeuse seems to be returning to a gas and surface environment similar to the one observed in Dec. 2018,” they write, “but with smoother structures, maybe
due to the unusual amount of dust recently formed during the GDE in the line of sight.”

Case closed?

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Even Early Galaxies Grew Hand-in-Hand With Their Supermassive Black Holes

Within almost every galaxy there is a supermassive black hole. This by itself implies some kind of formative connection between the two. We have also observed how gas and dust within a galaxy can drive the growth of galactic black holes, and how the dynamics of black holes can both drive star formation or hinder it depending on how active a black hole is. But one area where astronomers still have little information is how galaxies and their black holes interacted in the early Universe. Did black holes drive the formation of galaxies, or did early galaxies fuel the growth of black holes? A recent study suggests the two evolved hand in hand.

It’s difficult to observe the complex dynamics of black holes and galaxies in the early cosmos, but one way to study them is to compare the mass of a galactic black hole with the mass of all the stars in its galaxy. This can be expressed as a ratio M_BH / M_* to see how it varies over time. This means measuring this ratio at ever-increasing redshifts, since the greater the redshift, the younger the galaxy.

For this study, the team looked at 61 galaxies with active galactic nuclei (AGNs) as identified by X-ray observations. The luminosity of the AGNs gives us an idea of the black hole’s mass. They then added JWST observations of these galaxies from the COSMOS-Web and PRIMER surveys. From these, they could get the infrared luminosity of the galaxies, which let them determine their total stellar mass.

The mass ratios of this study (red dots) compared to earlier studies. Credit: Tanaka, et al

The galaxies they observed have redshifts between z = 0.7 and z = 2.5, meaning that the galaxies are seen as they were 6 billion to 11 billion years ago. What they found is that galaxies and their black holes grow hand in hand. As the galaxy increases in mass, so does the black hole. The relationship is very roughly linear, though the ratio favors the black hole slightly at higher redshifts. For you math geeks, the team found the ratio varies as M_BH / M_* = (1 + z)^0.37. This means the black holes grow at a slightly slower rate than the galaxies.

Unfortunately, the uncertainty of this result is rather large. It will take more observations, particularly at the higher redshift end, to pin down the relation more precisely. But in the coming years, astronomers should be able to gather this data. This study shows that galaxies and their black holes grow at similar rates across billions of years. Future studies will help us understand the more subtle connections between them.

Reference: Tanaka, Takumi S., et al. “The M_BH-M_* relation up to z = 2 through decomposition of COSMOS-Web NIRCam images.” arXiv preprint arXiv:2401.13742 (2024).

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Webb Directly Images Two Planets Orbiting White Dwarfs

In several billion years, our Sun will become a white dwarf. What will happen to Jupiter and Saturn when the Sun transitions to become a stellar remnant? Life could go on, though the giant planets will likely drift further away from the Sun.

Stars end their lives in different ways. Some meet their end as supernovae, cataclysmic explosions that destroy any orbiting planets and even sterilize planets light-years away. But only massive stars explode like that.

Our Sun is not massive enough to explode as a supernova. Instead, it’ll spend time as a red giant. The red giant phase occurs when a star runs out of hydrogen to feed fusion. It’s a complicated process that astronomers are still working hard to understand. But red giants shed layers of material into space that light up as planetary nebulae. Eventually, the red giant is no more, and only a tiny, yet extraordinarily dense, white dwarf resides in the middle of all the expelled material.

Researchers think that some white dwarfs have debris disks around them, out of which a new generation of planets can form. But researchers have also wondered if some planets can survive as stars transition from the main sequence to red giant to white dwarf.

Researchers at the Space Telescope Science Institute, Goddard Space Flight Center, and other institutions have found what seem to be two giant planets orbiting two white dwarfs in two different systems. Their research is titled “JWST Directly Images Giant Planet Candidates Around Two Metal-Polluted White Dwarf Stars,” and it’s in pre-print right now. The lead author is Susan Mullally, Deputy Project Scientist for JWST.

Theoretical thinking shows that exoplanets should exist around white dwarfs. Outer planets beyond where the asteroid belt is in our Solar System should survive their star’s transition from the main sequence to a red giant to a white dwarf. But stars inside this limit will be engulfed by the red giant as it expands. In our Solar System, the Sun will likely completely engulf or tidally disrupt and destroy Mercury, Venus, and Earth. Maybe even Mars.

Artist’s impression of a red giant star. As these stars lose mass, they expand and can envelop planets that are too close. Credit: NASA/ Walt Feimer

Planets that survive this will likely drift further from the star since the star loses mass and its gravity weakens during the red giant phase.

But the problem is that it’s difficult to detect planets around white dwarfs. Despite pointed efforts, astronomers have only found a few planetary-mass objects orbiting white dwarfs.

As it stands now, Mullally and her colleagues have found two candidate planets around white dwarfs. They’re about 11.5 and 34.5 AU from their stars, which are 5.3 billion and 1.6 billion years old. If the planets are as old as the stars, then MIRI photometry shows that the planets are between 1 to 7 Jupiter masses. They could be false positives, but there’s only a 1 in 3,000 chance that that’s the case.

“If confirmed, these would be the first directly imaged planets that are similar in both age and separation
to the giant planets in our own solar system, and they would demonstrate that widely separated giant
planets like Jupiter survive stellar evolution,” the authors write.

If the researchers are correct, and the planets formed at the same time as the stars, this is an important leap in our understanding of exoplanets and the stars they orbit. It may also have implications for life on any moons that might be orbiting these planets.

But this discovery relates to another issue with white dwarfs: white dwarf metallicity.

Some white dwarfs appear to be polluted with metals, elements heavier than hydrogen and helium. Astronomers think that these metals come from asteroids in the asteroid belt, perturbed and sent into the white dwarf by giant planets. “Confirmation of these two planet candidates with future MIRI imaging would provide evidence that directly links giant planets to metal pollution in white dwarf stars,” the authors write.

Astronomers have found that up to 50% of isolated white dwarfs with hydrogen atmospheres have metals in their photospheres, the stars’ surface layer. These white dwarfs must be actively accreting metals from their surroundings. The favoured source for these metals is asteroids and comets.

“In this scenario, planets that survive the red-giant phase occasionally perturb the orbits of asteroids and comets, which then fall in towards the WD,” the authors write.

This artist’s illustration shows rocky debris being drawn toward a white dwarf. Astronomers think that giant planets perturb smaller objects like asteroids and comets inside the WD’s Roche limit. They’re destroyed, and the debris is drawn onto the star’s surface. Image Credit: NASA, ESA, Joseph Olmsted (STScI)

Astronomers have struggled to find planets around WDs. The main methods of finding planets aren’t very effective around white dwarfs. The transit method used by Kepler and TESS is ineffective because WDs are so tiny and dim. The other method is the radial velocity method. It senses how a star wobbles due to a planet’s influence. It measures the change in the star’s spectrum due to the wobbling. However, WDs have nearly featureless spectra, making radial changes difficult to detect.

But now we have the JWST.

“JWST’s infrared capabilities offer a unique opportunity to directly image Jupiter-mass planets orbiting
nearby WDs,” the researchers write in their paper.

The JWST is powerful enough to directly image large planets around tiny stars without using a coronagraph, as long as the planets are far enough away from the star. “Taking advantage of JWST’s superb resolution, it is possible to directly image a planet at only a few au from nearby WDs without the use of a coronagraph,” Mullally and her colleagues explain.

Part of the effort in this work is identifying point sources. In astronomy, a point source is a single, identifiable source of light. Its opposite is a resolved source or an extended source. The researchers had to be confident that what they’re seeing around the white dwarfs are point sources, which are mostly likely planets in this case. “We expect these to appear as point sources that increase in brightness at longer wavelengths,” they write.

To determine if what they’re seeing are point sources, astronomers use a process called reference differential imaging. It’s a complex procedure, but basically, it involves subtracting the sources from the images. It’s especially effective at finding planets close to stars.

This figure from the research explains some of the findings. Each row is a separate white dwarf and planet candidate. In the top row, the large object in the north is a background galaxy unrelated to the research. The researchers went through a process of subtracting and then adding back in both the stars and the giant planet candidates. Image Credit: Mullally et al. 2024.

The figure above shows how the team worked with the images, subtracting both the white dwarf and the candidate planets and identifying the planets as point sources. “In both cases, the candidate is removed cleanly, indicating it is point-source in nature,” the authors write. The researchers examined four separate white dwarfs and only two of them have candidate exoplanets.

“If confirmed, these two planet candidates provide concrete observational evidence that outer giant planets like Jupiter survive the evolution of low-mass stars,” the authors write. Confirmation would also support the idea that 25%-50% of white dwarfs host large planets. That’s a big step forward in understanding.

But these results unfortunately can’t answer another question: are large planets responsible for sending debris onto the surface of white dwarfs? “The confirmation of these planets are not, however, sufficient to fully validate that large-mass giant planets are the driver of accretion without further observations,” writes Mullally and her co-authors.

An answer to that question can only come from observing more white dwarfs, especially with the JWST. Hopefully, we won’t have to wait long.

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Feast Your Eyes on 19 Face-On Spiral Galaxies Seen by Webb

If you’re fascinated by Nature, these images of spiral galaxies won’t help you escape your fascination.

These images show incredible detail in 19 spirals, imaged face-on by the JWST. The galactic arms with their multitudes of stars are lit up in infrared light, as are the dense galactic cores, where supermassive black holes reside.

The JWST captured these images as part of the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) programme. PHANGS is a long-running program aimed at understanding how gas and star formation interact with galactic structure and evolution. One of Webb’s four primary science goals is to study how galaxies form and evolve, and the PHANGS program feeds that effort. The VLT, ALMA, the Hubble, and now the JWST have all contributed to it.

But Webb’s images are the juiciest.

“Webb’s new images are extraordinary. They’re mind-blowing even for researchers who have studied these same galaxies for decades.”

Janice Lee, Project Scientists, Space Telescope Science Institute.

The JWST can see in both near-infrared (NIR) and mid-infrared (MIR) light. That means it reveals different details, and more details, than even the powerful Hubble Space Telescope, which operates in visible light, UV light, and a small portion of infrared light.

This is NGC 4254 (Messier 99), a spiral galaxy about 50 million light-years away. It has a peculiarity to it, as one spiral arm is normal looking, and one is extended and less tightly wound. Though not a starburst galaxy, it forms stars three times as fast as other similar galaxies. This rapid star formation rate may have been triggered by interaction with another galaxy about 280 million years ago. With the JWST’s help, the PHANGS program will help astronomers understand NGC 4254’s history. Image Credit: NASA, ESA, CSA, STScI, Janice Lee (STScI), Thomas Williams (Oxford), PHANGS Team

In these JWST high-resolution images, the red colour is gas and dust emitting infrared light, which the JWST excels at seeing. Some of the images have bright diffraction spikes in the galactic center, which are caused by an enormous amount of light. That can indicate that a supermassive black hole is active, or it could be from an extremely high concentration of stars.

“That’s a clear sign that there may be an active supermassive black hole,” said Eva Schinnerer, a staff scientist at the Max Planck Institute for Astronomy in Heidelberg, Germany. “Or, the star clusters toward the center are so bright that they have saturated that area of the image.”

The diffraction spike in the center of NGC 1365 is a telescope artifact caused by an enormous amount of light in a compact region. It’s caused by either the active supermassive black hole or tightly grouped stars in the galactic centre. NGC 1365 is a double-barred spiral galaxy about 74 million light-years away. Image Credit: NASA, ESA, CSA, STScI, Janice Lee (STScI), Thomas Williams (Oxford), PHANGS Team

Stars near a galaxy’s center are typically much older than stars in the arms. The further a star is from the galactic center, the younger it typically is. The younger stars appear blue and have blown away the cocoon of gas and dust that they spawned in.

This is NGC 2835, a spiral galaxy about 35 million light-years away that has four or five spiral arms. Blue dots are very young stars that have blown away nearby gas and dust with their powerful UV light. Orange/red clumps are where even younger stars reside. They’re still surrounded by gas and dust. Several background galaxies are visible in the image. Image Credit: NASA, ESA, CSA, STScI, Janice Lee (STScI), Thomas Williams (Oxford), PHANGS Team

Orange clumps indicate even younger stars. They’re still wrapped in their blanket of gas and dust and are still actively accreting material and forming. “These are where we can find the newest, most massive stars in the galaxies,” said Erik Rosolowsky, a professor of physics at the University of Alberta in Edmonton, Canada.

The new images were released alongside some of the Hubble’s views of the same galaxies. These highlight how observing different wavelengths of light reveals or obscures different details in the galaxies. In the PHANGS observing program, different telescopes have observed galaxies in visible light, infrared light, UV light, and radio.

A Hubble Space Telescope image of NGC 628 (left) and the same galaxy as imaged by the JWST (right.) Both images are grand and inspiring and full of information, but the JWST image provides more detail. Large bubble-shaped gaps between concentrations of gas and dust are visible. In some of the images, those could be caused by supernovae. Image Credit: NASA, ESA, CSA, STScI, Janice Lee (STScI), Thomas Williams (Oxford), PHANGS Team

Since the human eye can’t see infrared, different visible colours are assigned to different wavelengths of light in order to make the images meaningful. In the JWST image of NGC 628 above, the galaxy’s center is filled with old stars that emit some of the shortest wavelengths of light the telescope can detect. They’ve been given a blue colour to make them visible. In the Hubble image, the same region is more yellow and washed out. The region emits the longest wavelengths of light that the Hubble can sense, so it has different colour assignments than the JWST.

Janice Lee is a project scientist at the Space Telescope Science Institute in Baltimore. She spoke for all of us when she said, “Webb’s new images are extraordinary. They’re mind-blowing even for researchers who have studied these same galaxies for decades. Bubbles and filaments are resolved down to the smallest scales ever observed and tell a story about the star formation cycle.”

This is NGC 1672, a spiral galaxy about 60 million light-years away. It may be a type II Seyfert galaxy, though astronomers aren’t totally certain. It has both a bright nucleus and a surrounding starburst region. Image Credit: NASA, ESA, CSA, STScI, Janice Lee (STScI), Thomas Williams (Oxford), PHANGS Team

These galaxies are all spiral galaxies like the Milky Way, meaning their massive arms define them. The spiral arms are more like waves that travel through space rather than individual stars moving collectively. Astronomers study the arms because they can provide key insights into how galaxies build, maintain, and shut off star formation. “These structures tend to follow the same pattern in certain parts of the galaxies,” Rosolowsky added. “We think of these like waves, and their spacing tells us a lot about how a galaxy distributes its gas and dust.”

The spiral galaxy NGC 1566 is about 60 million light-years away in the constellation Dorado. NGC is interacting with smaller member galaxies in its neighbourhood. It’s an active galaxy, meaning its nucleus emits a lot of light that doesn’t come from stars. Instead, it probably comes from the supermassive black hole at the center. NGC 1566 is extensively studied due to its proximity, orientation, its strong spiral arms and its active galactic nucleus. Image Credit: NASA, ESA, CSA, STScI, Janice Lee (STScI), Thomas Williams (Oxford), and the PHANGS team

Ever since it began science operations, the JWST has given astronomers an overwhelming flow of data that will fuel research for years and decades to come. These beautiful images are just a part of a larger data release that includes a catalogue of about 100,000 star clusters. “The amount of analysis that can be done with these images is vastly larger than anything our team could possibly handle,” said the University of Alberta’s Erik Rosolowsky. “We’re excited to support the community so all researchers can contribute.”

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A Magnetohydrodynamic Drive Could Lead to Fuel Stations on Mars

Within the next fifteen years, NASA, China, and SpaceX plan to send the first crewed missions to Mars. In all three cases, these missions are meant to culminate in the creation of surface habitats that will allow for many returns and – quite possibly – permanent human settlements. This presents numerous challenges, one of the greatest of which is the need for plenty of breathable air and propellant. Both can be manufactured through electrolysis, where electromagnetic fields are applied to water (H₂O) to create oxygen gas (O₂) and liquid hydrogen (LH₂).

While Mars has ample deposits of water ice on its surface that make this feasible, existing technological solutions fall short of the reliability and efficiency levels required for space exploration. Fortunately, a team of researchers from Georgia Tech has proposed a “Magnetohydrodynamic Drive for Hydrogen and Oxygen Production in Mars Transfer” that combines multiple functionalities into a system with no moving parts. This system could revolutionize spacecraft propulsion and was selected by NASA’s Innovative Advanced Concepts (NIAC) program for Phase I development.

The proposal comes from Alvaro Romero-Calvo, an assistant professor at the Georgia Institute of Technology, and his colleagues from the Georgia Tech Research Corporation (GTRC). The system employs a magnetohydrodynamic (MHD) electrolytic cell, which relies on electromagnetic fields to accelerate electrically conductive fluid (in this case, water) without any moving parts. This allows the system to extract and separate oxygen and hydrogen gas in microgravity, removing the need for forced water recirculation and the associated equipment (i.e., pumps or centrifuges).

As a specialist in low-gravity science, fluid mechanics, and magnetohydrodynamics, Romero-Calvo and his team have spent many years investigating the applications of MHD systems for spaceflight. The need for a dedicated study to assess the concept’s feasibility and integration into a suitable oxygen production architecture ultimately motivated their proposal. In a previous study, Romero-Calvo and co-author Dr. Katharina Brinkert (a professor of Chemistry at the University of Warwick) noted how water harvested in situ would reduce vehicle launch masses.

However, they also noted that operating this kind of machinery in microgravity presented many unknowns, most of which are not addressed by current research. In particular, they stressed how the absence of buoyancy in microgravity results in major technical challenges, like the need to detach and collect oxygen and hydrogen bubbles, which was traditionally addressed using forced water recirculation loops. However, they argued, this leads to liquid management devices composed of multiple elements and moving parts, which are complex, inefficient, and unreliable in space. As Romero-Calvo explained in a recent Georgia Tech news release:

“The idea of using MHD forces for liquid pumping is explored in the 1990 thriller The Hunt for Red October, where a stealth soviet submarine powered by an MHD drive defects to the United States. Although it’s fun to see Sean Connery playing the role of a Soviet submarine commander, the truth is that submarine MHD propulsion is very inefficient. Our concept, on the contrary, works in the microgravity environment, where the weak MHD force becomes dominant and can lead to mission-enabling capabilities.”

Instead of traditional recirculation loops, the proposed MHD system relies on two distinct mechanisms to separate oxygen and hydrogen from water. The first comes from diamagnetic forces, which arise in the presence of strong magnetic fields and result in a magnetic buoyancy effect. Second, there are Lorentz forces, which are a consequence of the imposition of a magnetic field on the current generated between two electrodes. As Romero-Calvo noted in their proposal paper:

“Both approaches can potentially lead to a new generation of electrolytic cells with minimum or no moving parts, hence enabling human deep space operations with minimum mass and power penalties. Preliminary estimations indicate that the integration of functionalities leads to up to 50% mass budget reductions with respect to the Oxygen Generation Assembly architecture for a 99% reliability level. These values apply to a standard four-crew Mars transfer with 3.36 kg oxygen consumption per day.”

Two CubeSats communicated and then maneuvered toward one another in a recent technology demonstration. Credit: NASA

If successful, this HMD system would enable the recycling of water and oxygen gas in long-term space travel. Romero-Calvo and other colleagues at the Daniel Guggenheim School of Aerospace Engineering at Georgia Tech demonstrated in another paper that this technology could also have applications for water-based SmallSat propulsion and other mission profiles where ISRU is a must. At present, Romero-Calvo and his colleagues have formulated the concept and have developed analytical and numeral models.

The next step will involve the team and their partners at Giner Labs (a Massachusetts-based electrochemical R&D firm) conducting feasibility studies. Over the next nine months, they will receive $175,000 to explore the system’s overall viability and technology readiness level. These will consist primarily of computational studies but will include prototypes testing key technologies here on Earth. As a Phase I proposal, they will also be eligible to compete for Phase II funding worth $600,000 for a two-year study.

An early demonstrator of this technology was tested aboard the 24th flight of the New Sheperd (NS-24), an uncrewed mission that launched on December 19th, 2023. With support from Blue Origin and the American Society for Gravitation and Space Research (ASGSR), Romero-Calvo’s team tested how magnets electrolyzer water in microgravity conditions. The data from this flight and the forthcoming tests will inform an HMD electrolyzer prototype and could lead to a system integrated aboard future space missions. Said Romero-Calvo:

“We were studying the fundamental magnetohydrodynamic flow regimes that arise when we apply a magnetic field to water electrolyzers in spaceflight conditions,” Romero-Calvo explained. “The Blue Origin experiment, in combination with our current collaboration with Prof. Katharina Brinkert’s group at the University of Warwick, will help us predict the movement of oxygen bubbles in microgravity and it hints at how we can build a future water electrolyzer for humans.”

Further Reading: NASA, Georgia Tech

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Atmosphere Pressure Changes Could Explain Mars Methane

One ongoing mystery on Mars is the sporadic detection of atmospheric methane. Since 1999 detections have been made by Earth-based observatories, orbital missions, and on the surface by the Curiosity Rover. However, other missions and observatories have not detected methane at all, and even when detected, the abundances appear to fluctuate seasonally or even daily.

So, where does this intermittent methane come from? A group of scientists have proposed an interesting theory: the methane is being sucked out of the ground by changes in pressure in the Martian atmosphere. The researchers simulated how methane moves underground on Mars through networks of underground fractures and found that seasonal changes can force the methane onto the surface for a short time.

In their paper, published in the Journal of Geophysical Research: Planets, the scientists say their simulations predict short-lived methane pulses prior to sunrise for Mars’ upcoming northern summer period, which is a candidate time frame for Curiosity’s next atmospheric sampling campaign.

“Our work suggests several key time windows for Curiosity to collect data,” said John Ortiz, a graduate student at Los Alamos National Laboratory who led the research team. “We think these offer the best chance of constraining the timing of methane fluctuations, and (hopefully) down the line bringing us closer to understanding where it comes from on Mars.”

The presence of methane (CH4) in the Martian atmosphere is of great interest to planetary scientists and exobiologists because it could indicate present or past microbial life. Or, it could also be related to nonbiological processes, such as volcanism or hydrothermal activity.

The problem with detecting methane is that it doesn’t last long. Once released into the atmosphere, it can be quickly destroyed by natural atmospheric processes. Therefore, any methane detected in Mars’ atmosphere means it must have been released recently, which only adds to the intrigue.

On Earth, most methane is produced by living creatures such as microorganisms in sedimentary strata, or in the guts of ruminants (cows, sheep, deer, etc.). For methane produced through abiotic or non-living processes, there is a high likelihood it could have been produced millions or even billions of years ago, lying trapped in underground rock formations.

But still, finding methane on Mars is a big deal because of the potential for biological sources, such as methanogenic microbes.

This graphic is the result of an analysis that gives a percentage chance of the methane originating in each grid square centered on Gale Crater. Image Credit: Giuranna et al. (2019)

In 2004, the Mars Express Orbiter (MEO) detected methane in the Martian atmosphere. In 2013 and 2014 Curiosity detected spikes in methane in the atmosphere at Gale Crater. Interestingly, MEO detected a methane spike again, at the same location that Curiosity did, only one day later.

Ortiz and his team wanted to better understand Mars’ methane levels, and used high-performance computing clusters to simulate how methane travels through networks of underground fractures, and then released into the atmosphere when driven by atmospheric pressure fluctuations. They also modeled how methane is adsorbed onto the pores of rocks, which is a temperature-dependent process that may contribute to the methane level fluctuations.

The team said their simulations predicted methane pulses from the ground surface into the atmosphere just before the Martian sunrise in the planet’s northern summer season, which just recently ended. This corroborates previous rover data suggesting that methane levels fluctuated not only seasonally, but also daily. With these insights, the Curiosity rover team can figure out when and where to look for methane, which could aid in the rover’s main goal, searching for signs of life.

“Understanding Mars’ methane variations has been highlighted by NASA’s Curiosity team as the next key step towards figuring out where it comes from,” Ortiz said. “There are several challenges associated with meeting that goal, and a big one is knowing what time of a given sol (Martian day) is best for Curiosity to perform an atmospheric sampling experiment.”

Paper: “Sub-diurnal methane variations on Mars driven by barometric pumping and planetary boundary layer evolution.” Journal of Geophysical Research: Planets. DOI: 10.1029/2023JE008043
LANL press release

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NASA Gives us an Update on its Long-term Plans for the Moon and Mars

Going to Mars is a major step in space exploration. It’s not a quick jaunt nor will it be easy to accomplish. The trip is already in the planning stages, and there’s a good chance it’ll happen in the next decade or so. That’s why NASA and other agencies have detailed mission scenarios in place, starting with trips to the Moon. Recently, NASA updated its “Moon to Mars Architecture” documents, including a closer look at some key decisions about Mars exploration.

Those decisions cover a wide gamut of challenges to living and working on the Red Planet. NASA planners narrowed them down to these key areas: science priorities, number of crew members on the first trip, how many on each follow-up trip, number of crew members per Mars location, Mars surface power generation technologies, what kinds of missions will be sent (the “target state”), and establishing what they call a “loss of crew risk” posture. That last one involves making the right decisions about missions based on risk to the crew’s health and performance.

NASA Plans for the Moon and Mars

Why create a mission architecture for the Moon and Mars? Essentially, anybody going to these other worlds needs a mutually agreed-upon “roadmap” that plans the explorations and technologies needed. That’s why NASA created its first Moon to Mars objectives in 2022 and has been refining them ever since. The agency’s roadmap includes feedback from a wide swath of society. Members of academia, U.S. industry, international partners, and the NASA workforce all contributed to the project.

“Our new documents reflect the progress we’ve made to define a clear approach to exploration and lay out how we’ll incorporate new elements as technologies and capabilities in the U.S. and abroad mature,” said Catherine Koerner, associate administrator, Exploration Systems Development Mission Directorate at NASA Headquarters in Washington. “This process is ensuring that everything we are doing as an agency and together with our partners is focused on achieving our overarching exploration goals for the benefit of all.”

The Key Decisions Regarding Mars Exploration

In a white paper published along with the Moon to Mars Architecture document, NASA explains key areas of concern when it comes specifically to Mars exploration. The first is science. It’s the main reason for going the both the Moon and Mars, and its needs will drive almost all other considerations. It will determine the resources needed, including crew numbers, payloads, technology deliveries, and power and communications infrastructure, and contingencies for possible accidents or other challenges.

An artist’s concept of Mars explorers and their habitat on the Red Planet. Courtesy NASA.

Once the science is determined, planners can decide on crew needs for the first and subsequent missions. As the white paper states, “…a series of focused science exploration missions to different landing sites would favor one architecture. Establishing a permanent, fixed base from which astronauts could conduct many surface missions supporting diverse and evolving exploration activities would favor a very different architecture.”

From there, planners will figure out the “cadence” of the missions and crew deployments. How often do we send missions and how many people will go? Just as an example, let’s say that the first mission will land in Jezero Crater, near the Perseverance rover. NASA could use its data to determine further science exploration at the site. That will drive the best placement for habitats and other infrastructure, and the type of mission will dictate the number of crew members needed.

Those decisions will then drive the infrastructure and technology needed for each step. Science stations need power to do the science, but also to sustain the habitats for the science teams. If those teams travel across the surface, their rovers will need power, fuel, and possibly replacement parts. Crew members themselves will need to be able to grow food, use local resources to extract fuel and water, and otherwise maintain safe living conditions. And, these are just the first steps in the long-term exploration of Mars, enabled by what people learn about living and working on the Moon.

Why Does NASA Want a Moon to Mars Plan?

While it may seem sexy to send people directly to Mars without any intervening stops at the Moon, NASA and other agencies want a measured approach. The idea to use the Moon as a stepping stone to Mars is not new. The Moon makes a good “training base” of sorts where we can “practice” with the technologies and techniques of living on another world. In addition, it offers a unique environment for astronomy and planetary science exploration. Astronauts learn in an environment close to Earth and if something dire happens to them, rescue is not far away.

Artist’s impression of astronauts on the lunar surface, as part of the Artemis Program. Credit: NASA

These ideas underlie the planning for the upcoming Artemis missions to the lunar surface. There’s supposed to be a gateway orbiting the Moon, to which astronauts and equipment will fly. Then, from there, materials and people head to the Moon to explore various sites, and begin the complex tasks of exploration and habitat construction. That set of missions will establish the foundation for scientific exploration, and land a diverse set of people on the lunar surface, all in cooperation with international partners. Ultimately, everything they learn on the Moon will prepare people for the leap to Mars.

The Moon to Mars mission architectural plans unite both lunar and Mars exploration in one timeline, identifying technologies and capabilities needed to accomplish each step. They are living documents, updated every year to reflect changes in any aspect of mission planning and technology.

For More Information

NASA Shares Newest Results of Moon to Mars Architecture Concept Review
Moon to Mars Architecture
Key Mars Architecture Decisions (PDF)

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There’s Less Dark Matter at the Core of the Milky Way

Science really does keep you on your toes. First there was matter and then there were galaxies. Then those galaxies had more stuff in the middle so stars further out were expected to move slowly, then there was dark matter as they actually seemed to move faster but now they seem to be moving slower in our Galaxy so perhaps there is less dark matter than we thought after all! 

Let’s start with dark matter.  It is a strange and mysterious form of matter that doesn’t really seem to behave in any way like normal matter. It doesn’t emit light, absorb or reflect it so is to all intents invisible, hence its name. It’s thought that about 27% of the Universe is made up of dark matter but the only way we can detect it is its gravitational effect on passing light and other matter. Despite mounting evidence for its existence, we have still yet to actually detect particles that make up dark matter, whatever they are. 

Physicists at MIT (the Massachusetts Institute of Technology) have measured the speed of stars in the Milky Way galaxy and found that those further out to the edge are moving slower than expected. This suggests, rather surprisingly that the core of the milky way may be lighter in mass than first thought and thus contain less dark matter. 

The team used data from Gaia and APOGEE (Apache Point Observatory Galactic Evolution Experiment) to plot the velocity of stars against their distance. This enabled them to generate a rotation curve that shows how fast matter rotates at a given distance from the centre of a galaxy. Interpreting graphs like these allow astronomers to estimate how much dark matter there is.

Artist impression of ESA’s Gaia satellite observing the Milky Way (Credit : ESA/ATG medialab; Milky Way: ESA/Gaia/DPAC)

This was quite in contrast to earlier observations since the 1970’s that revealed a hint of dark matter distribution. Measurements of previous galaxies showed that stars were moving around the centre at a fairly constant velocity with distance from centre. The only way this can be explained is dark matter. This work was pioneered by Vera Rubin from the Carnegie Institution in Washington and was supported by multiple observations from other astronomers in the following years. 

The efforts to measure galactic rotation have focussed on other galaxies rather than our own. It’s actually quite difficult to achieve the same in a galaxy that you live in but undaunted; Xiaowei Ou, Anna-Christina Eilers, and Anna Frebel set about the task. Their initial observations came from Gaia data but used APOGEE data to refine their results. They were able to measure distances of more than 33,000 stars out to a distance of 30 kiloparsecs (97,846 light years). The data was then incorporated into a model of circular velocity to estimate the velocity of stars given the location of all other stars in the galaxy. This gave them an updated and refined rotation curve. 

The curve their work revealed showed a more rapid decline over distance rather than the shallow decline they expected. Stars further out are moving slower than expected and so there is less matter in the centre of our galaxy. We can observe the ‘normal’ or baryonic matter but it requires less dark matter to account for the observations. Further research is now required to explore other galaxies like the Milky Way and perhaps, change our view of the amount of dark matter in the Universe. 

Source : Study: Stars travel more slowly at Milky Way’s edge

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Plants Growing in Space are at Risk from Bacterial Infections

I have spent the last few years thinking, perhaps assuming that astronauts live off dried food, prepackaged and sent from Earth. There certainly is an element of that but travellers to the International Space Station have over recent years been able to feast on fresh salad grown in special units on board. Unfortunately, recent research suggests that pathogenic bacteria and fungi can contaminate the ‘greens’ even in space.

It’s been at least three years that astronauts have been able to eat fresh lettuce and other leafy items along with tortillas and powdered coffee.. Specially designed chambers on board allow them to grown plants under carefully controlled temperature, water and lights to ensure a successful harvest.  There is however an issue that the ISS is a relatively closed environment and so it is easy for bacteria and fungi to spread and astronauts to get ill. 

The International Space Station stretches out in an image captured by astronauts aboard the SpaceX Crew Dragon Endeavour during a fly-around in November 2021. Credit: NASA

A paper just published in Scientific Reports and NPJ Microgravity and authored by a team led by Noah Totsline explores what happens with lettuce grown under ‘simulated’ weightless environments (the device known as a clinostat rotate them so that plants did not know which way was up or down). This was achieved by being gently rotated. Plants it seems though, are pretty good at sensing gravity using their roots. The team found that plants under these conditions were more prone to infection than those on Earth in particular Salmonella.

One of the main lines of defence for plants is their stomata. These are tiny pores in the leaves, much like the pores in our skin, that close to defend when an environmental stress is detected, such as bacteria.  The team exposed plants in their micro-gravitational environment to find the plants opened the stomata instead of closing them. 

The team went a step further and introduced a natural bacteria known as UD1022 which usually helps to protect plants. In the clinostat however, it failed to help the plant to protect itself from other more harmful bacteria.

The research was not just an interesting scientific problem but does solve real world problems. Space is slowly opening up with more and more non-astronauts becoming astronauts and travelling into space and this is only going to increase. As SpaceX and the like press ahead with the commercialisation of space travel we absolutely must find a way to grow and farm sustainable and healthy food instead of prepackaged snacks if we are to become a truly space fairing civilisation. 

We are some way away from that of course but this is step one in a long journey. Sadly it is not as simple a task as sterilising the seeds since their could easily be microbes in the environment on board the ISS (or other space craft that come in the future) and perhaps it is these that pose the greatest risk. The team are now looking at ways to genetically modify plants to help them cope in the microgravity of space.

Source : PROBLEMS WITH ROCKET SALAD

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Is the Habitable Zone Really Habitable?

The water that life knows and needs, the water that makes a world habitable, the water that acts as the universal solvent for all the myriad and fantastically complicated chemical reactions that make us different than the dirt and rocks, can only come in one form: liquid.

The vast, vast majority of the water in our universe is unsuitable for life. Some of it is frozen, locked in solid ice on the surface of a world too distant from its parent star or bound up in a lonely, wayward comet. The rest is vaporized, existing as a state of matter where molecules lose their electron companions, boundless and adrift through the great nebular seas that dot the galaxies, or ejected completely into the great voids between them. Either way, that water exists only one molecule at a time, at a temperature of over a million degrees yet its density so low that you could pass through it and mistake it for the cold, hard vacuum of space itself.

No, for water to be liquid it must exist in special place around a star, not too cold for it turn to ice, not too hot for it to turn to gas. It must lay within what astronomers call the habitable zone, or, if they’re feeling playful, the Goldilocks zone.

The habitable zone is different for every star throughout the galaxy, because no two stars are alike. The smallest red dwarfs are barely a tenth the mass of the Sun, with luminosities a thousand times weaker. The largest are great beasts, a hundred solar masses or more, so bright they can be seen from thousands of light-years away by the unaided eye. Around each star a simple iron law holds, the fact that the intensity of light, and all the warmth and comfort that light brings with it, diminishes with the square of the distance from the source. An object twice as far away will experience a quarter of the brightness; at a distance of four times that drops to a sixteenth, and so on. That is why Pluto, despite only sitting about 30 times further away from the Sun than the Earth, is forced to experience never-ending dim twilight, even at the height of its day.

Too far from a star and the radiant temperatures are too cold, and any water freezes. Too close, and the water slips its bonds, free to roam as a gas. In between, in a special band determined by the star’s mass, age, and brightness, sits the habitable zone, where a planet is capable – yes, merely capable – of hosting water in its liquid state on its surface.

For our own Sun, the habitable zone stretches from just within the orbit of Venus to just beyond the orbit of Mars. Three planets perfectly situated within the warm embrace of our Sun, and yet only one has life. What happened? What made our planet so special, or so lucky? It’s impossible to say for sure, because the potential of habitability is not a promise.

There is, however, one other place where we know liquid water can exist. Ironically, it’s in the frozen moons of the outer solar system. There, under surfaces of frozen ice a hundred kilometers thick sit globe-spanning liquid water oceans, with more liquid water than exists on the surface of the Earth. There the habitability isn’t given by the rays of the Sun, but from their molten cores emanating heat, driven by the gravitational warping of the giant planets they orbit. Life could certainly find a purchase there, in places of darkness that the Sun never can touch, even though there worlds are not, according to the traditional definition, habitable.

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NASA Wants to Put a Massive Telescope on the Moon

As part of the Artemis Program, NASA intends to establish all the necessary infrastructure to create a “sustained program of lunar exploration and development.” This includes the Lunar Gateway, an orbiting habitat that will enable regular trips to and from the surface, and the Artemis Base Camp, which will permit astronauts to remain there for up to two months. Multiple space agencies are also planning on creating facilities that will take advantage of the “quiet nature” of the lunar environment, which includes high-resolution telescopes.

As part of this year’s NASA Innovative Advance Concepts (NIAC) Program, a team from NASA’s Goddard Space Flight Center has proposed a design for a lunar Long-Baseline Optical Imaging Interferometer (LBI) for imaging at visible and ultraviolet wavelengths. Known as the Artemis-enabled Stellar Imager (AeSI), this proposed array of multiple telescopes was selected for Phase I development. With a little luck, the AeSI array could be operating on the far side of the Moon, taking detailed images of stellar surfaces and their environments.

The proposal was made by Kenneth Carpenter and his colleagues at NASA Goddard Space Flight Center (GSFC). Carpenter is the Hubble Operations Project Scientist at GSFC and the ground system scientist for the Nancy Grace Roman Space Telescope (RST). As they note in their proposal, NASA’s return to the Moon offers several significant opportunities for him-impact scientific research. Not the least of these is the potential for creating observatories that take advantage of the “radio quiet” environment and extended periods of darkness on the far side of the Moon.

Artist’s illustration of a radio telescope inside a crater on the Moon. Credit: NASA/JPL-Caltech

Due to the tidally locked nature of its orbit, where one side of the Moon is always facing toward Earth, the Moon’s day/night cycle lasts for 14 days. This means a “lunar day” consists of two weeks of continuous sunlight, while a lunar night consists of two weeks of continuous darkness. At the same time, the Moon’s airless environment means that any observations by optical telescopes will not be subject to atmospheric interference. This makes the far side of the Moon a pristine environment for conducting high-resolution interferometric imaging, a method where multiple telescopes collect light to look for patterns of interference.

Astronomers extract data from these patterns to create a detailed picture of celestial objects that are difficult to resolve with conventional telescopes. This same technique allowed the Event Horizon Telescope (EHT), a global network of radio telescopes, to acquire the first image of a black hole ever taken. According to the team, a lunar interferometry array has immense scientific potential and could be built incrementally to limit construction costs:

“This can resolve the surfaces of stars, probe the inner accretion disks surrounding nascent stars and black holes, and begin the technical journey towards resolving surface features and weather patterns on the nearest exoplanets. A fully developed facility will be large and expensive, but it need not start that way. The technologies can be developed and tested with 2 or 3 small telescopes on short baselines. Once the technology is developed, baselines can be lengthened, larger telescopes can be inserted, and the number of telescopes can be increased. Each of these upgrades can be accomplished with minimal disruption to the rest of the system.”

Despite these advantages, the team notes how previous studies on interferometers in space concentrated on designs for free-flying arrays. This was largely due to the 2003-2005 NASA Vision Missions Studies that examined the trade-offs between free-flying space concepts and kilometer-sized interferometers built on the lunar surface. The study concluded that it was better to pursue space-based free-flyers, given the absence of pre-existing human infrastructure on the lunar surface that could provide power and regular maintenance.

Illustration of NASA astronauts on the lunar South Pole. Mission ideas we see today have at least some heritage from the early days of the Space Age. Credit: NASA

However, with the Artemis Program, Carpenter and his team argue that this situation is now changing. With the completion of surface habitats, transportation, drilling, and power facilities planned for the coming years, now is a good time to investigate the possibility of building interferometers on the lunar surface. “Our study of a lunar surface-based interferometer will be a huge step forward to larger arrays on both the moon and free-flying in space, over a wide variety of wavelengths and science topics,” they write. “It will determine, given the current and anticipated state of our space technology and human exploration plans, whether it is better to pursue designs for the lunar surface or for deep space.”

They further envision that a lunar interferometer will lead to advancements in astrophysics, like the study of stellar magnetic activity, the nuclei of active galaxies, and the dynamics of cosmological phenomena on many scales. The design and construction of such a facility will address key engineering concerns, like the best way to incorporate variable-length optical lines, the best configurations for the telescopes, and the optimal mirror size for meeting both technical and scientific goals. They also hope to create a plan for maintaining and expanding the facility over time using a mix of human and robotic support.

Beyond that, the anticipated benefits include technical advances that will enable a UV-optical interferometer and space-based missions capable of imaging black holes (similar to the EHT), searching for biosignatures, and directly imaging rocky exoplanets around other stars. Carpenter and his colleagues also anticipate that the creation of a major facility on the Moon, in conjunction with the Artemis Program’s human exploration goals, will generate tremendous public interest and engagement:

“Finally, this effort will make people dream again – and remember that we can do great things, even in [the] face of difficult times. Our study will help keep the focus on the grandeur of the Universe and what humans can do if they work hard together. Our project will excite generations of future Science, Technology, Engineering, Art, and Mathematics (STEAM) workers, who will be inspired by this bold vision.”

Further Reading: NASA

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New Types of Hidden Stars Seen for the First Time

In the early days of telescopic astronomy, you could only focus on one small region of the sky at a time. Careful observations had to be done by hand, and so much of the breakthrough work centered around a particular object in the sky. A nebula or galaxy, quasar or pulsar. But over the years we’ve been able to build telescopes capable of capturing a wide patch of sky all at once, and with automation, we can now map the entire sky. Early sky surveys took years to complete, but many modern sky surveys can look for changes on the order of weeks or days. This ability to watch for changes across the sky is changing the way we do astronomy, and it is beginning to yield some interesting results. As a case in point, an infrared sky survey is revealing hidden stars we hadn’t noticed before.

In a series of papers published in the Monthly Notices of the Royal Astronomical Society, the authors have analyzed data from a decade-long survey called the Visible and Infrared Survey Telescope (VISTA). VISTA allows astronomers to keep an eye on hundreds of millions of stars at infrared wavelengths. In these works, the team combed through the observations to focus on about 200 stars that showed the most dramatic shifts in brightness. These transient changes are important because they can reveal the subtle dynamics of stars.

Artist’s impression of an eruption in the disc of matter around a newborn star. Credit: Philip Lucas/University of Hertfordshire

One goal of the studies was to look for very young stars. Stars in the earliest moments of transition toward becoming true fusion-powered stars. And within their selected stars they found 32 erupting protostars. All of them experienced a rapid increase of at least a factor of 40, and some brightened as much as a factor of 300. The outbursts lasted for months or years, and they seem to occur within the disk of matter surrounding the young stars. Based on the dynamics, these bursts can accelerate the growth of young stars, but they could also make it more difficult for planets to form. They refer to these turbulent protostars as squalling newborns.

The team also found a surprise. Deep within the center of our galaxy, they found 21 red giant stars with dramatic brightness changes. They turned out to be a new type of red giant known as old smokers. The center of our galaxy is rich with heavy elements, so these red giants have a high metalicity. As they age, they can cast off clouds of dust that can obscure the star for a time. So the star temporarily fades from view and then re-brightens as the clouds disperse. This discovery could change our understanding of how heavy elements are released into the galaxy to be used by new stars.

Reference: Lucas, P W, et al. “The most variable VVV sources: eruptive protostars, dipping giants in the nuclear disc and others.” Monthly Notices of the Royal Astronomical Society 582.2 (2024): 1789–1822.

Reference: Guo, Zhen, et al. “Spectroscopic confirmation of high-amplitude eruptive YSOs and dipping giants from the VVV survey.” Monthly Notices of the Royal Astronomical Society 582.2 (2024): 1769–1788.

Reference: Peña, Carlos Conteras, et al. “On the incidence of episodic accretion in Class I YSOs from VVV.” Monthly Notices of the Royal Astronomical Society 582.2 (2024): 1823–1840.

Reference: Guo, Zhen, et al. “Multiwavelength detection of an ongoing FUOr-type outburst on a low-mass YSO.” Monthly Notices of the Royal Astronomical Society 582.2 (2024): L115–L122.

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The Improbable Origins of Life on Earth

We do not yet know how, where, or why life first appeared on our planet. Part of the difficulty is that “life” has no strict, universally agreed-upon definition.

Normally this is not an issue, as the vast majority of life is most definitely alive, and only biologists interested in the extreme edges – viruses, prions, and the like – need to worry about precise classifications. But to study the origins of life we must, by necessity, examine a process that takes non-living matter and fundamentally changes it. Presumably this process happened in stages, with fits and starts along the way, and so the line between uncoordinated chemical reactions and the beginnings of vibrancy must be blurred.

It’s helpful here to present at least a simple working definition of life, not to rewrite the biology textbooks, but so that at least we can properly frame the discussion of life’s origins. And for those purposes a simple statement will suffice: life is that which is subject to Darwinian evolution. That is, life experiences natural selection, that unceasing pressure that chooses traits and characteristics to pass down to a new generation through the simple virtue of their survivability. If the trait contributes in some way, even circuitously, to the survivability of an organism and its ability to reproduce, it persists. All else is discarded (or, at best, gets carried unceremoniously along for the ride).

Earth is the only known place in the solar system, in the galaxy, in the entire universe where Darwinian evolution takes place.

To succeed at evolution and separate itself from mere chemical reactions, life must do three things. First, it must somehow store information, such as the encoding for various processes, traits, and characteristics. This way the successful traits can pass from one generation to another.

Second, life must self-replicate. It must be able to make reasonably accurate copies of its own molecular structure, so that the information contained within itself has the chance to become a new generation, changed and altered based on its survivability.

Lastly, life must catalyze reactions. It must affect its own environment, whether for movement, or to acquire or store energy, or grow new structures, or all the many wonderful activities that life does on a daily basis.

By interacting with its environment, making copies of itself, and storing information (like how to interact with the environment and make copies of itself), life can evolve, growing in complexity and specialization over geologic time, from humble molecules to conscious minds capable of peering into its own shrouded origins.

In the modern era, with billions of years of practice behind it, life on Earth has evolved a dizzying array of chemical and molecular machines to propagate itself – a menagerie so complex and interconnected that we do not yet fully understand it. But a basic picture has emerged. Put exceedingly simply (for I would hate for you to mistake me for a biologist), life accomplishes these tasks with a triad of molecular tools.

One is the DNA, which through its genetic code stores information using combinations of just four molecules: adenine, guanine, cytosine, and thymine. The raw ability of DNA to store massive amounts of information is nothing short of a miracle; our own digital system of 1’s and 0’s (invented because it’s much simpler to tell if a circuit is on or off than some stage in-between) is the closest comparison we can make to DNA’s information density. Natural languages don’t even earn a place on the chart.

The second component is RNA, which is intriguingly similar to DNA but with two subtle, but significant, differences: RNA swaps out thymine for uracil in its codebase, and contains the sugar ribose, which is one oxygen atom short of the deoxyribose of DNA. RNA also stores information but, again speaking only in generalities, has the main job of reading the chemical instructions stored in the DNA and using that to manufacture the last member of the triad, proteins.

“Proteins” is a generic catch-all term for the almost uncountable varieties of molecular machines that do stuff: they snip apart molecules, bind them back together, manufacture new ones, hold structures together, become structures themselves, move important molecules from one place to another, transform energy from one form to another, and so on.

Proteins have one additional function: they perform the job of unraveling DNA and making copies of it. Thus the triad completes all the functions of life: DNA stores information, RNA uses that information to manufacture proteins, and the proteins interact with the environment and perform the self-replication of DNA. This cycle allows living organisms to experience the gift of evolution.

And this cycle is, as I said, gloriously complex and obviously the result of billions of years of fine-tuning and refinement. The interconnected nature of DNA, RNA, and proteins means that it could not have sprung up ab initio from the primordial ooze, because if only one component is missing then the whole system falls apart – a three-legged table with one missing cannot stand.

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