Ages ago in its youth, Mars appeared much like Earth. It was a warm planet with lakes, rivers, and vast seas. It had a thick atmosphere with clouds and rain. One major difference is that the atmosphere was rich with carbon dioxide instead of oxygen. Then about 3.5 billion years ago much of the atmosphere disappeared, and we haven’t understood how. A new study in Science Advances suggests that the waters of Mars may have been the key, and much of the ancient atmosphere may be locked in the surface of the red planet.
The authors center their paper on a clay mineral known as smectite. On Earth smectite is produced through tectonic activity. As tectonic plates are uplifted they can drag material from the mantle to the surface, some of which is this kind of clay. One characteristic of smectite is that it’s full of little folds. Nooks and crannies if you will, that can trap carbon dioxide for billions of years. In an earlier study the team demonstrated how smectite on Earth helped prevent our world from becoming a greenhouse planet by pulling carbon dioxide out of our early atmosphere. It’s a process still going on today. Mars doesn’t experience tectonic activity, but smectite can be found all over Mars, and the authors wondered if it might solve the mystery of the Martian atmosphere.
The processes that captured the Martian atmosphere. Credit: Murray & Jagoutz
The challenge was to figure out how so much smectite formed on Mars. Rather than uplifting tectonic plates it is a series of chemical reactions. The authors suggest that water on Mars seeped through olivine, a magnesium iron silicate common on Earth, Mars, and even asteroids. The iron in olivine would bind with the water’s oxygen and release hydrogen. This hydrogen would then react with carbon dioxide to form methane. Over time this process would transform the olivine into smectite, which would trap methane and carbon dioxide. Based on their calculations the team argues that 80% of the ancient atmosphere is now trapped in the Martian clay, leaving the thin atmosphere we see today.
If this model is true, it could be a boon for future Martian explorers. Not only will there be plenty of water found beneath the surface, there will also be large quantities of methane. The solution to the problems of water and fuel could be right under the feet of those first explorers, trapped in the nooks and crannies of common clay.
I’ve often stated that planets come in a wide range of sizes but rarely do I find myself stating they come in a wide range of shapes too! The discovery of WASP-107b is a case in point since this planet is the size of Jupiter but only a tenth of its mass. But there’s more… Using the James Webb Space Telescope a team of astronomers have accurately identified that the planet has an east-west asymmetry in its atmosphere, in other words, it’s lopsided. It is tidally locked to the star and on one side, the atmosphere seems to be inflated compared to the other.
Planets orbiting other stars are known as exoplanets. WASP-107b is one such planet in orbit about a star 200 light years away in the constellation of Virgo. The first exoplanet detection was confirmed in 1992 and since then over 5,000 alien planets have been identified. A multitude of different techniques are used to hunt them down from searching for dips in light from distant stars to analysing the spectra of a star. A wide variety of planet systems have been found from Earth-like possibly habitable planets to great big gas giants like Jupiter. With the new generation of space telescopes like the JWST it is now possible to study the atmosphere of exoplanets to learn even more about them.
Artist impression of the James Webb Space Telescope
A team of astronomers from the University of Arizona have been using the JWST with an international group of researchers to study WASP-107b. They discovered the east-west asymmetry of the planet as it passed in front of its host star just like the Moon does during a solar eclipse.
The shape of the planet is an atmospheric phenomenon but of course when it comes to gas giants like Jupiter that’s pretty much referring to the planet itself. It’s not just a physical asymmetry though as there are temperature and cloud property differences between the eastern and western hemisphere. It’s now important to explore the asymmetry observed to learn more about the dynamics of the planet and whether it’s a unique phenomenon.
“Icy and Rocky Worlds” is a new exoplanet infographic by Slovak artist and space enthusiast Martin Vargic. It’s available as a wall poster at his website. Image Credit and Copyright: Martin Vargic
One element of the planet which is cause for investigation and likely cause is that it’s tidally locked to the star. The force of gravity from the star and the force of gravity on the planet have acted upon each other to lock one face of the planet to the star. This means one hemisphere is constantly illuminated and warmed by the star while the other hemisphere is permanently night! Tidal locking is not unique to WASP-107b though so if this is the cause then the asymmetry should be common.
To make their finding, the team used a technique known as transmission spectroscopy. In this technique, observations are made of the starlight as it passes through the atmosphere of the planet during transit events. As the light passes through atmospheric gasses, the presence of different gasses interacts with the light in different ways that can be seen during spectral analyses.
What does make WASP-107b unique is low gravity and low density giving rise an atmosphere that is somewhat over-inflated compared to other alien worlds of this mass. This is the first time such an asymmetry has been seen so it will be interesting to see how unique this fascinating world really is.
Venus is often described as a hellscape. The surface temperature breaches the melting point of lead, and though its atmosphere is dominated by carbon dioxide, it contains enough sulfuric acid to satisfy the comparison with Hades.
But conditions throughout Venus’ ample atmosphere aren’t uniform. There are locations where some of life’s building blocks could resist the planet’s inhospitable nature.
Among the rocky planets, Venus has by far the largest atmosphere by volume. So, while its surface is inhospitable, its atmosphere has regions that are the most Earth-like of anywhere else in the Solar System. Scientists have wondered if life could survive in parts of the planet’s upper atmosphere, and the discovery of the potential biomarker phosphine (though it was later disproved) generated more interest.
Some research suggests that life could exist within Venus’ voluminous clouds. Image Credit: Abreu et al. 2024.
One reason Venus keeps coming up in discussions around habitability is that it’s accessible, whereas exoplanets aren’t. Venus is easily reached, and we currently have one orbiter in place, the Japanese Akatsuki spacecraft. Three other missions to Venus are planned for the mid-2030s: NASA’s Veritas and DAVINCI and the ESA’s EnVision.
Nobody is convinced we’ll find life on Venus. But the planet can teach us a lot about chemistry and biology and their limits.
In new research, a team of scientists tested different building blocks under Venus-like conditions to see if they can withstand the planet’s perilous nature. The research is “Simple lipids form stable higher-order structures in concentrated sulfuric acid.” The lead author is Daniel Duzdevich from the Department of Chemistry at the University of Chicago. The paper is in pre-print now and has been submitted to the journal Astrobiology.
Venus’ surface isn’t a candidate for habitability. But regions in its atmosphere may be. The issue is that much of Venus’ sulfuric acid is concentrated in discrete clouds rather than diffused throughout its atmosphere.
“The Venusian surface is sterilizing, but the cloud deck includes regions with temperatures and pressures conventionally considered compatible with life. However, the Venusian clouds are thought to consist of concentrated sulfuric acid,” the authors explain.
Cloud structure in the Venusian atmosphere in 2016, revealed by observations in the two ultraviolet bands by Akatsuki. Credit: Kevin M. Gill
They wanted to test if any of life’s “fundamental features” could withstand Venus’ challenging environment. Can any of life’s chemistry resist sulfuric acid?
“Organic chemistry in concentrated sulfuric acid is rarely studied yet surprisingly rich, with recent work supporting the notion that complex organic molecules, including amino acids and nucleobases can be stable in this unusual solvent,” the authors write.
If simple organic molecules can remain stable in sulfuric acid, it’s an interesting observation in favour of life. But it takes more complexity than that, and that’s what this research focuses on.
“One fundamental feature of life is cellularity: the differentiation of “inside” (the contents of a cell, including information, molecules, and all their interactions) and “outside” (the environment), in addition to a mechanism for communication and exchange between the two,” Duzdevich and his co-researchers write.
The researchers focused on lipids, the membranes that define cells. Lipids are the foundation of cellular structure, not only as membranes between cells but also as membranes that create distinct parts of the interior of cells. “The cell membrane is especially important in extreme environments because it must help maintain the homeostasis of the intracellular environment against otherwise harsh external conditions,” the authors write.
The researchers performed lab experiments to determine whether lipids can withstand Venus’ harsh environment. They asked two questions: Can simple lipids resist decomposition by sulfuric acid, and can the lipids form stable higher-order structures like they do in cells?
The researchers placed masses of lipids in vials and exposed them to different concentrations of sulfuric acid and measured each vial at specific intervals. Their results show that some lipids can survive exposure to the acid and even form structures.
This figure from the research shows the vesicle-like structures that formed after concentrated sulfuric acid was added to solid lipids. Each panel is a different region of the same sample taken on the same day. Subsequent images showed that the structures remained intact even after seven days. Image Credit: Duzdevich et al. 2024.
Interested readers can explore the detailed chemistry for themselves.
In summary, the results suggest that stable membranes can form and persist in the presence of sulfuric acid. Life uses water as a solvent because it’s a polar molecule, can form networks of hydrogen bonds, has a high heat capacity, and, of course, is abundant on Earth. But it’s not abundant everywhere.
Critically, this study shows that some aspects of the chemistry of life don’t require water as a solvent. Instead, they can tolerate and use sulfuric acid as a solvent. “Here, we show the unexpected stability of complex membranous structures in another polar solvent: concentrated sulfuric acid,” the authors write.
What does this mean for exoplanet habitability and astrobiology?
“Concentrated sulfuric acid as a planetary solvent could be widespread on exoplanets, either on exo-Venuses or on other rocky planets that are desiccated as a result of the stellar activity of their host star,” the researchers explain.
And, of course, sulfuric acid is present in large amounts at Venus.
“Concentrated sulfuric acid is also present in our immediate planetary vicinity as a dominant liquid in the clouds of Venus, further emphasizing its importance for planetary science, planetary habitability, and astrobiology,” the authors write.
The question of whether life could somehow survive in Venus’ clouds is one that won’t go away. We’re new at the astrobiology game, and we’re simply not in a position to rule things out. It might seem far-fetched, but science is an evidence game, and evidence can be surprising.
This study doesn’t present evidence that can answer the question—big questions like this are answered incrementally—but it does present an intriguing result.
“By demonstrating the stability of lipid membranes in this aggressive solvent, we have taken a significant step forward in exploring the potential habitability of the concentrated sulfuric acid cloud environment on Venus,” the authors conclude.
The reason we call dark matter dark isn’t because it’s some shadowy material. It’s because dark matter doesn’t interact with light. The difference is subtle, but important. Regular matter can be dark because it absorbs light. It’s why, for example, we can see the shadow of molecular clouds against the scattered stars of the Milky Way. This is possible because light and matter have a way to connect. Light is an electromagnetic wave, and atoms contain electrically charged electrons and protons, so matter can emit, absorb and scatter light. Dark matter isn’t electrically charged. It has no way to connect with light, and so when light and dark matter meet up they simply pass through each other.
All of our observations suggest that dark matter and light only have gravity in common. When dark matter is clustered around a galaxy, for example, its gravitational tug can deflect light. Because of this we can map the distribution of dark matter in the Universe by observing how light is gravitationally lensed around it. We also know that dark and regular matter interact gravitationally. The tug of dark matter causes galaxies to gather together into superclusters. But an unanswered question is whether dark and regular matter only interact gravitationally. If an atom and dark matter particle intersected, would they really just pass through each other?
Since we haven’t directly observed dark matter particles we can only speculate, but most dark matter models argue that gravity is the only common link with light and regular matter. Dark and regular matter clump around each other, but they don’t collide and merge like interstellar clouds. But a new study suggests the two do interact, which could reveal subtle aspects of the mysterious stuff.
The study looks at six ultrafaint dwarf galaxies, or UFDs. They are satellite galaxies near the Milky Way that seem to have far fewer stars than their mass would suggest. This is because they are mostly made of dark matter. If regular and dark matter only interact gravitationally, then the distribution of stars in these small galaxies should follow a certain pattern. If dark and regular matter interact directly, then this distribution will be skewed.
To test this the team ran computer simulations of both scenarios. They found that in the non-interacting model the distribution of stars should become more dense in the center of the UFDs and more diffuse at the edges. In the interacting model the stellar distribution should be more uniform. When they compared these models with observations of the six galaxies, they found the interacting model was a slightly better fit.
So it seems dark and regular matter interact in ways beyond their gravitational tugs. There isn’t enough data to pin down the exact nature of the interaction, but the fact there is any interaction at all is a surprise. It means that our traditional models of dark matter are at least partly wrong. It may also point the way toward new methods of detecting dark matter directly. In time we may finally solve the mystery of this dark, but not entirely invisible, material.
We have known that water ice exists on the Moon since 1998. These large deposits are found in the permanently shadowed craters around the polar region. The challenge is how to get it since shadowed craters are not the best place for solar powered vehicles to operate. A team of engineers have identified a design for an ice-mining vehicle powered by americium-241. With a half-life of 432 years, this element is an ideal power source for a vehicle to operate in the dark for several decades.
Ice in the polar regions of the Moon is of vital importance for our future space explorations, not just lunar visits but as we stretch our legs in the Solar System. Its thought to be ancient material deposited by comets or formed by interactions with solar wind. It is expensive to take materials to the Moon so harvesting on site is far more efficient. Ice on the Moon can provide drinking water, oxygen for breaking and even hydrogen for rocket fuel. Surveys suggest something in the region of 600 billion kilograms of ice deposited at the lunar poles.
Exposed water ice (green or blue dots) in lunar polar regions and temperature. Credit: Shuai Li
The challenge facing future lunar harvesting missions is that operations in the permanently shadowed regions (or PSRs as they have been called) cannot be powered by solar panels as is often the case. The environment is cold too, in the region of 40K, that’s -233?C and at those temperatures special power considerations are required.
A team of researchers have been exploring the use of Radioisotope Power Systems (RPS) to provide thermal and electrical power systems. These power systems have been used before during deep space missions for example Voyager and New Horizons. They work by generating electricity using the heat that is released from the natural decay of a radioactive isotope usually plutonium-238.
Artist rendition of Voyager 1 entering interstellar space. (Credit: NASA/JPL-Caltech)
The team led by Marzio Mazzotti from the University of Leicester have explored an ice-mining rover using power generated by the radio activate decay fo Americium-241. It has a half-life of 432 years which means it takes 432 years for half of a sample of Americium to decay. During this time, half of the atoms in the substance will transform into a different element. Using this power source will provide a stable power supply for an ice-mining rover in the darkness of the lunar polar craters for decades.
Apollo 17 commander Eugene Cernan with the lunar rover in December 1972, in the moon’s Taurus-Littrow valley. Credit: NASA
Using a radioisotope power system is not new however the team came upon the idea that the excess heat that is not used can be used to thermally mine ice from samples of lunar material. The rover would be fitted with a sublimation plate that would turn any ice deposits into a gas which would be collected in a cold trap.
The team developed a model of its Thermal Management System and tested it for icy regolith (the fine dusty lunar surface) material with a water ice content of 0-10 vol %. Their simulations showed that it is possible to mine ice using thermal techniques in the PSR of the Moon using an RPS (I had to really concentrate writing that sentence!) powered lunar rover.
It’s no secret that spending extended periods in space takes a toll on the human body. For years, NASA and other space agencies have been researching the effects of microgravity on humans, animals, and plants aboard the International Space Station (ISS). So far, the research has shown that being in space for long periods leads to muscle atrophy, bone density loss, changes in vision, gene expression, and psychological issues. Knowing these effects and how to mitigate them is essential given our future space exploration goals, which include long-duration missions to the Moon, Mars, and beyond.
However, according to a recent experiment led by researchers at Johns Hopkins University and supported by NASA’s Johnson Space Center, it appears that heart tissues “really don’t fare well in space” either. The experiment consisted of 48 samples of human bioengineered heart tissue being sent to the ISS for 30 days. As they indicate in their paper, the experiment demonstrates that exposure to microgravity weakens heart tissue and weakens its ability to maintain rhythmic beats. These results indicate that additional measures must be taken to ensure humans can maintain their cardiovascular health in space.
Heart tissues within one of the launch-ready chambers. Credit: Jonathan Tsui
Previous research has shown that astronauts returning to Earth from the ISS suffer from a myriad of health effects consistent with certain age-related conditions, including reduced heart muscle function and irregular heartbeats (arrhythmias), most of which will dissipate over time. However, none of this research has addressed what happens at the cellular and molecular level. To learn more about these effects and how to mitigate them, Kim and his colleagues sent an automated “heart-on-a-chip” platform to the ISS for study.
To create this payload, the team relied on human-induced pluripotent stem cells (iPSCs), which can become many types of cells, to produce cardiomyocytes (heart muscle cells). These resulting tissues were placed in a miniaturized bioengineered tissue chip designed to mimic the environment of an adult human heart. The chips would then collect data on how the tissues would rhythmically contract, imitating how the heart beats. One set of biochips was launched aboard the SpaceX CRS-20 mission to the ISS in March 2020, while another was kept on Earth as a control group.
Once on the ISS, astronaut Jessica Meir tended the experiment, changing the liquid nutrients surrounding the tissues once each week while preserving tissue samples at specific intervals so gene readout and imaging analyses could be conducted upon their return to Earth. Meanwhile, the experiment sent real-time data back to Earth every 30 minutes (for 10 seconds at a time) on the tissue samples’ contractions and any irregular beating patterns (arrhythmias).
“An incredible amount of cutting-edge technology in the areas of stem cell and tissue engineering, biosensors and bioelectronics, and microfabrication went into ensuring the viability of these tissues in space,” said Kim in a recent Hub news release.
When the tissue chambers returned to Earth, he and his colleagues continued to maintain and collect data from the samples to see if there was any change in their abilities to contract. In addition to losing strength, the muscle tissues developed arrhythmias, consistent with age-related heart conditions. In a healthy human heart, the time between beats is about a second, whereas the tissue samples lasted nearly five times as long – though they returned to nearly normal once returned to Earth.
The team further found that the tissue cell’s protein bundles that help them contract (sarcomeres) were shorter and more disordered than those of the control group, another symptom of heart disease. What’s more, the mitochondria in the tissue samples grew larger and rounder and lost the characteristic folds that help them produce and use energy. Lastly, the gene readout in the tissues showed increased gene production related to inflammation and an imbalance of free radicals and antioxidants (oxidative stress).
This is not only consistent with age-related heart disease but also consistently demonstrated in astronauts’ post-flight checks. The team says these findings expand our scientific knowledge of microgravity’s potential effects on human health in space and could also advance the study of heart muscle aging and therapeutics on Earth. In 2023, Kim’s lab followed up on this experiment by sending a second batch of tissue samples to the ISS to test drugs that could help protect heart muscles from the effects of microgravity and help people maintain heart function as they age.
Meanwhile, the team continues to improve its tissue-on-a-chip system and has teamed up with NASA’s Space Radiation Laboratory to study the effects of space radiation on heart muscles. These tests will assess the threat solar and cosmic rays pose to cardiovascular health beyond Low Earth Orbit (LEO), where Earth’s magnetic field protects against most space radiation.
Now is the time to catch Comet A3-Tsuchinshan-ATLAS at dawn.
The window is now open. If skies are clear, set your alarm heading into this weekend to see Comet C/2023 A3 Tsuchinshan-ATLAS at dawn. We’re already seeing great views of the comet this week from southern observers and astronauts aboard the International Space Station. The visibility window is now even creeping up to the southern tier latitudes of the contiguous United States (CONUS). If fortune favors us, the comet could hit an easy naked eye magnitude +2 by next week, and forward scattering could even boost this into negative magnitudes… the rare term ‘daytime comet’ is even getting kicked around a bit in cometwatching circles.
But the span to see this comet will be brief indeed. For most northern hemisphere observers, the comet will be a bashful one, never reaching much more than 10 degrees above the eastern horizon about 45 minutes before sunrise on the week centered around September 29th.
Exposures of Comet A3 against the brightening dawn. Credit: Chris Schur
The Story of Comet A3 Tsuchinshan-ATLAS Thus Far
We wrote about prospects for this comet for Universe Today previously just last month. China’s Tsuchinshan (Purple Mountain) observatory and the automated ATLAS (Asteroid Terrestrial impact Last Alert System) survey discovered the comet on January 9th, 2023. I’ve seen the name abbreviated to simply ‘Comet A3’ or ‘Comet T-ATLAS’ in discussions on keystroke-conservative social media.
Likely a first-time visitor to the inner solar system from the distant Oort Cloud, the comet is on an orbit measured in millions of years. This may also be the one and only appearance of the comet in the inner solar system. That’s a good thing, in terms of dynamics and activity, as the comet may have never experienced the heat of the inner solar system in the past. The comet could well head towards permanent ejection from the solar system after perihelion.
Key dates coming right up include when the comet reaches perihelion this coming Friday on September 27th at 0.391 Astronomical Units (AU, 36.4 million miles or 58.6 million kilometers) from the Sun, just interior to Mercury’s aphelion point. The comet then makes its closest Earth approach on October 12th, at 0.556 AU distant.
Comet A3 Tsuchinshan-ATLAS will become more difficult to catch after October 7th, as it heads in to the Solar Heliospheric Observatory’s (SOHO) LASCO C3 field of view and approaches less than 15 degrees elongation from the Sun. The comet makes a second evening reappearance mid-month, which will most likely be less than favorable as it heads away from us and back out of the inner solar system. We could, however, see something interesting in late October (if the comet survives perihelion) as the tail precedes ahead of the outbound comet.
Chris Schur caught the comet from Payson, Arizona (with a narrow 10 minute window!) on the morning of September 23rd. Credit: Chris Schur.
How the Comet is Performing Now
The comet seemed to be headed towards the long rolls of ‘great comets that weren’t’ this past summer, as it stalled at +10th magnitude. Now, the trend seems to have shifted, as the comet is over-performing versus expectations. As of writing this, the comet stands at +3rd magnitude and is rapidly brightening.
We’re already seeing signs of two tails (one dust and one ion) forming in this week’s images of the comet. Forward scattering may help boost the visibility of the comet next week, as all those dust particles reach a maximum illumination angle as seen from our Earthly vantage point in early October. The comet’s orbit passes edge-on from our vantage point on October 14th. The comet will seem to hang stationary low in the dawn next week, as it loops towards us, and then crosses between the Earth and the Sun.
Comet T-ATLAS as imaged from Tivoli Farm, Namibia on September 22nd (note the fan of the comet’s second tail off to the left). Credit: Gerald Rhemann.
How to See the Comet
The October apparition will be a tricky one for sure. A good strategy is to use binoculars and start sweeping low to the eastern horizon about an hour before local sunrise. The +1st magnitude star Regulus (Alpha Leonis) will make a good ‘guide star’ to find the comet. The star will be about an outstretched hand’s width to the observer’s lower right. The comet pairs with the slim waning crescent Moon on the morning of September 30th, making for a grand photo-op. That same Moon is headed towards an annular solar eclipse on October 2nd.
The view on the morning of September 30th. Credit: Starry Night Edu Software.
Clouded out? We feel your frustration here in eastern Tennessee, as clouds from approaching hurricane Helene move inland this coming weekend. Astronomer Gianluca Masi will also carry the comet live on the evening of October 9th.
Comet C/2023 A3 Tsuchinshan-ATLAS from September 24th. Credit: The Virtual Telescope Project.
“It (Comet T-ATLAS) survived and so far, it looks brighter than expected.” Astrophotographer Eliot Herman told Universe Today. “I still don’t think it will be amazing when it can be seen when dark enough… I am thinking maybe March 2013 Comet (C/2011 L4) PanSTARRS level – which was visible to the eye and pretty nice with a camera.”
We can only hope for a bright comet as depicted by astronomer Charles Piazzi Smyth’s painting of the Great Daytime Comet of 1843:
Astronauts aboard the International Space Station already caught the comet from their vantage point in low Earth orbit this week. NASA astronaut Matthew Dominick produced this fine animation:
Comet A3 Tsuchinshan-ATLAS is teasing us with the recent memories of two other dawn comets. Remember P1 McNaught in 2006-2007 and W3 Lovejoy in 2011-2012? Both beat the odds, and went on to become fine comets, ahead of expectations.
Comet McNaught imaged from Villa Alemana, Chile in January 2007. Credit: Garcia Ruben/Wikimedia Commons/Public Domain.
As always with comets, a caveat is in order: several factors will conspire against your cometary quest. First: as noted, the comet will appear very low to the horizon. This means it will fight against the thick murk of the atmosphere and the brightening twilight sky. Secondly, comets are intrinsically dark objects, with a low surface brightness or albedo… remember Rosetta’s views of Comet 67P Churumov-Gerasimenko? Lastly, like deep sky objects, all of that precious magnitude gets dispersed over an apparent surface area. This makes a +2 magnitude comet much fainter looking versus a +2nd magnitude star. During F3 NEOWISE’s 2020 apparition, I could juuuust start to convince myself that it was naked eye when it reached around +1st magnitude.
Comet C/2023 A3 (Tsuchinshan-ATLAS) is finally here ! ???I captured this image this morning at 09:22 UTC from @LCOAstro in Atacama desert in Chile ?? The view was absolutely spectacular ! The clouds were constantly moving just above the horizon, but we got really lucky when the… pic.twitter.com/AoClHkatFr
We had two recent comets perform very similar to Comet A3 Tsuchinshan-ATLAS. In 2020, Comet F3 NEOWISE became a fine naked eye comet at dawn, wowing early morning observers. On the flip side, 2023’s Comet P1 Nishimura flirted with naked eye brightness, but never really became a general crowd pleaser.
Clear skies on your hunt this coming week, to see what’s most likely to be the best comet of 2024.
The most likely way we will discover life on a distant exoplanet is by discovering a biosignature. This can be done by looking at the atmospheric spectra of a world to discover the spectral pattern of a molecule that can only be created through biological processes. While it sounds straightforward it isn’t. The presence of simple molecules such as water and oxygen don’t prove life exists on a planet. It’s true that Earth’s atmosphere is oxygen rich thanks to life, but geological activity can also produce large quantities of oxygen. And as a new study shows, some molecules we’ve long thought to be biological in origin may not be.
Ideally astronomers would love to find evidence of a really complex molecule such as chlorophyll. But there isn’t likely to be tons of chlorophyll in an atmosphere, so the spectral pattern would be faint, and even if it were clear the pattern is complex and hard to distinguish. So astronomers generally focus on simpler but unique molecules. One of these molecules is dimethyl sulfide, (CH3)2S or DMS for short. It is only produced by phytoplankton on Earth, so it would be a strong indicator of life. Or so we thought.
In this new work the team was able to synthesize DMS and other sulfur-based molecules in the lab abiotically. While that doesn’t prove the same process can happen in the wild, the team went on to show how DMS could be formed on a world with a thick organic haze. We know such planets exist because Saturn’s moon Titan is just such a world. If, for example, Titan happened to be closer to the Sun, the ultraviolet radiation would be significant enough to trigger the chemical reactions necessary to create DMS. If Titan were in Earth’s orbit, a distant alien race would detect DMS in the atmosphere of a planet in the Sun’s habitable zone. It would look like a slam dunk, but Titan would still be toxic to life as we know it.
How a biosignature molecule might form naturally. Credit: Reed, et al
But Titan might have some presence of exotic life, which is another conclusion to this study. While the authors show that the presence of DMS or similar molecules wouldn’t prove life exists on a world, they argue that it would indicate a strong potential for life. Basically, a warm planet with the kind of rich organic haze in its atmosphere would necessarily have the kind of complex organic molecules life needs to evolve. If DMS exists on a world, then the potential for life exists at the very least.
While this study shows we will need to be careful about treating particular molecules as biosignatures, it also supports what exo-biologists have known for some time. The discovery of life on another world isn’t likely going to happen as a single great eureka moment. What is more likely is that a handful of planets will have chemical markers that support the possibility of life. Over time as we find more candidate biomarkers in their atmospheres we will be ever more confident that life exists.
When a massive star explodes as a supernova, it does more than release an extraordinary amount of energy. Supernovae explosions are responsible for creating some of the heavy elements, including iron, which is blasted out into space by the explosion. On Earth, there are two accumulations of the iron isotope Fe60 in sea-floor sediments that scientists trace back about two or three million years ago and about five to six million years ago.
The explosions that created the iron also dosed Earth with cosmic radiation.
“Life on Earth is constantly evolving under continuous exposure to ionizing radiation from both terrestrial and cosmic origin,” the authors write. Terrestrial radiation slowly decreases over billions of years. But not cosmic radiation. The amount of cosmic radiation that Earth is exposed to varies as our Solar System moves through the galaxy. “Nearby supernova (SN) activity has the potential to raise the radiation levels at the surface of the Earth by several orders of magnitude, which is expected to have a profound impact on the evolution of life,” they write.
The authors explain that the two million-year-old accumulation is directly from a supernova explosion, and the older accumulation is from when Earth passed through a bubble.
The bubble in the study’s title comes from a particular type of star called OB stars. OB stars are massive, hot, and short-lived stars that usually form in groups. These stars emit powerful outflowing winds that create “bubbles” of hot gas in the interstellar medium. Our Solar System is inside one of these bubbles, called the Local Bubble, which is almost 1,000 light-years wide and was created several million years ago.
An artist’s conception of the hot local bubble. Image Credit: NASA
The Earth entered the Local Bubble about five or six million years ago, which explains the older Fe60 accumulation. According to the authors, the younger Fe60 accumulation from two or three million years ago is directly from a supernova.
“It is likely that the 60Fe peak at about 2-3 Myr originated from a supernova occurring in the Upper Centaurus Lupus association in Scorpius Centaurus (~140 pc) or the Tucana Horologium association (~70 pc). Whereas the ~ 5-6 Myr peak is likely attributed to the Solar System’s entrance into the bubble,” the authors write.
The left panel shows the Local Bubble and nearby stellar associations, while the right panel shows their galactic coordinates. The right panel also shows a new Galactic bubble discovered in 2018. It’s likely the remnant of an SN that exploded in Upper Centaurus Lupus. Image Credit: Nojiri et al. 2024.
The Local Bubble is not a quiet place. It took multiple supernovae to create it. The authors write that it took 15 SN explosions over the last 15 million years to create the LB. “We know from the reconstruction of the LB history that at least 9 SN exploded during the past 6 Myrs,” they write.
The researchers took all the data and calculated the amount of radiation from multiple SNe in the LB. “It is not clear what would the biological effects of such radiation doses be,” they write, but they do discuss some possibilities.
This figure shows the average dose rate experienced at ground level as a function of the distance to the nearby SN. The average dose is calculated over the first 10 kyr (solid line) and over the first 100 kyr (dashed line) after the SN explosion. It’s not enough to trigger an extinction, but it could’ve driven species diversification. Image Credit: Nojiri et al. 2024.
The radiation dosage may have been strong enough to create double-strand breaks in DNA. This is severe damage and can lead to chromosomal changes and even cell death. But there are other effects in terms of the development of life on Earth.
“Double-strand breaks in DNA can potentially lead to mutations and jump in the diversification of species,” the researchers write. A 2024 paper showed that “the rate of virus diversification in the African Tanganyika lake accelerated 2-3 Myr ago.” Could this be connected to SN radiation?
“It would be appealing to better understand whether this can be attributed to the increase in cosmic-radiation dose we predict to have taking place during that period,” the authors tease.
The SN radiation wasn’t powerful enough to trigger an extinction. But it could’ve been powerful enough to trigger more mutations, which could lead to more species diversification.
Radiation is always part of the environment. It rises and falls as events unfold and as Earth moves through the galaxy. Somehow, it must be part of the equation that created the diversity of life on our planet.
“It is, therefore, certain that cosmic radiation is a key environmental factor when assessing the viability and evolution of life on Earth, and the key question pertains to the threshold for radiation to be a favourable or harmful trigger when considering the evolution of species,” the authors write in their conclusion.
Unfortunately, we don’t clearly understand exactly how radiation affects biology, what thresholds might be in place, and how they might change over time. “The exact threshold can only be established with a clear understanding of the biological effects of cosmic radiation (especially muons that dominate at ground level), which remains highly unexplored,” Nojiri and her co-authors write.
The study shows that, whether we can see it in everyday life or not, or even if we’re aware of it or not, our space environment exerts a powerful force on Earth’s life. SN radiation could’ve influenced the mutation rate at critical times during Earth’s history, helping shape evolution.
Without supernova explosions, life on Earth could look very different. Many things had to go just right for us to be here. Maybe in the distant past, supernova explosions played a role in the evolutionary chain that leads to us.
On June 6th, 2024, the fourth orbital test flight of the Starship successfully lifted off at 07:50 a.m. CT (08:50 a.m. EDT; 06:50 PDT) from SpaceX’s Starbase in Texas. This test was the first time the Starship (SN29) and Super Heavy (BN11) prototypes reentered Earth’s atmosphere and landed successfully. While the SN29 conducted a powered vertical landing before splashing down in the Indian Ocean, the BN11 executed a similar powered landing before splashing down in the Gulf of Mexico. In a recent tweet, Elon Musk shared a photo of the BN11 booster being pulled out of the sea.
News of the retrieval was posted via Elon Musk’s X account, where he hinted at the possibility of refurbishment and reuse, writing, “Fixer upper.” In addition to being the first flight test in which both vehicles made it back in one piece, this flight was also the first time that a Super Heavy booster simulated a landing at a “virtual tower.” In the future, SpaceX intends to retrieve its boosters by “catching” them with the Orbital Launch Mount tower at their Starbase facility. This is expected to occur for the first time during the fifth integrated flight test, scheduled for no earlier than late November 2024.
The flight test was originally scheduled for September but was delayed by the Federal Aviation Administration (FAA) until November due to environmental complaints and the licensing process. According to statements by the FAA and SpaceX, the company was already authorized to conduct multiple flights using the same mission profile they followed for the fourth flight test. However, adding an attempted “catch” has led the FAA to conduct a more thorough review of the flight and the launch facility.
Researchers have developed a set of hexagon-shaped robotic components that can be snapped together into larger and larger structures. Each one of the component hexagons is made of rigid plates that serve as its exoskeleton. Driven by electricity, the plates can change their shape, shifting from long and narrow to wide and flat at high speed. The combined structures are capable of jumping four times their own body height, then can shape-shift to roll extremely fast, or use multimodal actuation to crawl through confined spaces.
The robotic components were developed at the Max-Planck-Institute for Intelligent Systems (MPI-IS). The modules are made of six lightweight rigid plates made from glass fiber that form a hexagon. Magnets embedded into the plates allows for quick connection to other components as well as providing a shared electrical ground between the modules.
Individual HEXEL modules combine soft artificial muscles with rigid components for fast and large motions. Credit: Zachary Yoder / MPI-IS Ellen Rumley / MPI-IS
The design team integrated artificial “muscles” into the inner joints of the hexagons, called hydraulically amplified self-healing electrostatic (HASEL) muscles. Applying a high voltage to the module causes the muscle to activate, rotating the joints of the hexagon and changing its shape from long and narrow to wide and flat.
“Combining soft and rigid components in this way enables high strokes and high speeds. By connecting several modules, we can create new robot geometries and repurpose them for changing needs,” said Ellen Rumley, a visiting researcher from the University of Colorado Boulder, in a press release from MPI-IS. Rumley and Zachary Yoder, who are both Ph.D. students working in the Robotic Materials Department, are co-first authors of a new paper, “Hexagonal electrohydraulic modules for rapidly reconfigurable high-speed robots,” published in Science Robotics.
The modules are reconfigurable, with an easy process of attaching or detaching the modules. Chains of modules can be rapidly connected and can operate from one voltage source. The modules can each have their own behaviors, which allows for various operations.
The team created a video to show the various configurations and behaviors that can be created with HEXEL modules. The modules can be seen rolling, dancing, jumping, crawling, and many other motions.
“In general, it makes a lot of sense to develop robots with reconfigurable capabilities,” said Yoder. “It’s a sustainable design option – instead of buying five different robots for five different purposes, we can build many different robots by using the same components. Robots made from reconfigurable modules could be rearranged on demand to provide more versatility than specialized systems, which could be beneficial in resource-limited environments.”
Noctilucent clouds were once thought to be a fairly modern phenomenon. A team of researcher have recently calculated that Earth and the entire Solar System may well have passed through two dense interstellar clouds causing global noctilucent clouds that may have driven an ice age. The event is thought to have happened 7 million years ago and would have compressed the heliosphere, exposing Earth to the interstellar medium.
Interstellar clouds are vast regions of gas and dust that flat between the stars inside galaxies. They are mostly made up of hydrogen along with a little helium and trace elements of heavier elements. They are a key part of the life circle of stars providing the materials for new stars to be formed and are seeded with elements after stars die. The clouds vary significantly in size, density and location and are an important part of the evolution of the Galaxy.
An annotated illustration of the interstellar medium. The solar gravity lens marks the point where a conceptual spacecraft in interstellar space could use our sun as a gigantic lens, allowing zoomed-in close-ups of planets orbiting other stars. Credits: Charles Carter/Keck Institute for Space Studies
Earth’s journey around the Galaxy is not for the impatient for it takes about 250 million years to complete one full orbit at a speed of 828,000 kilometres per hour. Currently the Solar System is located in the Orion Arm, one of the spiral arms of our Galaxy. During the journey, Earth travels through different regions, encountering stars and different densities of the interstellar medium. It experiences gravitational interactions with nearby stars and nebula sometimes exerting subtle interactions. Regardless of the immense journey, the stars of our Galaxy remain relatively unchanged over a human lifetime.
The Milky Way is a spiral galaxy with several prominent arms containing stellar nurseries swathed in pink clouds of hydrogen gas. The sun is shown near the bottom in the Orion Spur. Credit: NASA
A team of astronomers let by Jess A. Miller from the Department of Astronomy of Boston University have traced the path of the Sun back through time. In doing so, they have identified two occasions when the Earth and Solar System passed through two dense interstellar clouds. One of the crossings occurred 2 million years ago, the other 7 million years ago. Exploring the properties of the clouds, the team assert that the clouds are dense enough that they could compress the solar wind to inside the orbit of Earth.
The Solar Wind is a constant stream of charged particles, mostly electrons and protons that are emitted from the upper layer of the Sun’s atmosphere, the corona. The particles travel through the Solar System at speeds between 400 and 800 kilometres per second. The edge of our Solar System is defined as the point where the solar wind merges with the interstellar medium.
A composite image comprised of the Sun’s surface, corona, and digitally-added coronal loops rendered by Andrew McCarthy. (Credit: Andrew McCarthy)
Previous teams have analysed climate change events due to these interstellar medium interactions with similar findings. Global cooling has been the result with an ice age being triggered. The study by Miller and team have readdressed this very topic using modern technology and processes.
The team find that the interactions have indeed played a part in changes to the atmosphere of Earth. They find that levels of hydrogen in the upper atmosphere would have increased substantially. The newly acquired hydrogen would be converted to water molecules in the lower atmosphere and it would also have led to a reduction in mesospheric levels of ozone. These processes would have led to the appearance of global noctilucent clouds in the mesosphere. They would not have been permanent but may have blocked 7% of sunlight from reaching Earth, plunging our planet into an ice age.
Earth’s last half-billion years were action-packed. During that time, the climate underwent many changes. There have been changes in ocean levels and ice sheets, changes in the atmosphere’s composition, changes in ocean chemistry, and ongoing biological evolution punctuated with extinction events.
A record of Earth’s temperature over the last 485 million years is helping scientists understand how it all played out and illustrating what could happen if we continue to enrich the atmosphere with carbon.
The new temperature record is presented in research titled “A 485-million-year history of Earth’s surface temperature.” It’s published in Science, and the lead author is Emily Judd. Judd is from the Department of Paleobiology at the Smithsonian National Museum of Natural History.
“This research illustrates clearly that carbon dioxide is the dominant control on global temperatures across geological time.”
Jessica Tierney, University of Arizona
The new historical temperature comes from an effort named PhanDA, which stands for Phanerozoic Data Assimilation. PhanDA combined data from climate models with data from geology to determine how the climate has changed over the last nearly 500 million years. The Phanerozoic is Earth’s current geological eon, and it started 538.8 million years ago. It’s known for the proliferation of life, and its beginning is marked by the appearance of the hard shells of animals in the fossil record.
PhanDA is a mix of data and prior simulations by the scientific community. “This approach leverages the strengths of both proxies and models as sources of information, providing an innovative way to explore the temporal and spatial patterns in Earth’s climate across the Phanerozoic,” the researchers write in their paper. It allowed the researchers to reconstruct the climate more thoroughly.
This figure illustrates the data used to create PhanDA. A shows the temporal distribution of proxy data used in PhanDA. B shows the spatial distribution. C shows the range (gray band) and median (black line) of GMSTs within the prior model ensemble for each assimilated stage. Image Credit: Judd et al. 2024.
“This method was originally developed for weather forecasting,” said Judd. “Instead of using it to forecast future weather, here we’re using it to hindcast ancient climates.”
We’re blowing by atmospheric carbon benchmarks, and the Earth is warming. We’re now at over 420 ppm of CO2. The best way to understand what’s coming our way is by looking at the past.
“If you’re studying the past couple of million years, you won’t find anything that looks like what we expect in 2100 or 2500,” said co-author Scott Wing, the curator of paleobotany at the National Museum of Natural History. Wing’s research focuses on the Paleocene–Eocene Thermal Maximum, a period of dramatic global warming 55 million years ago. “You need to go back even further to periods when the Earth was really warm, because that’s the only way we’re going to get a better understanding of how the climate might change in the future.”
During the Paleocene-Eocene Thermal Maximum (PETM), a massive amount of carbon was emitted into the atmosphere and the oceans. The Earth’s temperature reacted swiftly, warming by between five and eight degrees Celsius in only a few thousand years. While a few thousand years might seem long compared to a human lifetime, it’s nearly instantaneous for the climate of an entire planet. It likely triggered the massive extinction of between 35% to 50% of benthic life. Fossils show that during this time, sub-tropical planets grew in the polar regions.
Many scientists think the PETM is the best analogue for what we’re facing today. No matter what we do with our emissions in the next several decades, much of the carbon humanity has released into the atmosphere since the Industrial Revolution will persist in the atmosphere for thousands of years.
Earth’s reconstructed Global Mean Surface Temperature for the past 485 million years. Blue rectangles show the maximum latitudinal ice extent, and orange dashed lines show the timing of the five major mass extinctions of the Phanerozoic. The five orange fishbone symbols mark mass extinctions. Image Credit: Judd et al. 2024.
PhanDA illustrates the unbreakable link between carbon and global warming. According to co-author Jessica Tierney, a paleoclimatologist at the University of Arizona, the link between the climate and carbon is undeniable. “This research illustrates clearly that carbon dioxide is the dominant control on global temperatures across geological time,” said Tierney. “When CO2 is low, the temperature is cold; when CO2 is high, the temperature is warm.”
While proof of the link between climate and carbon isn’t new, this long timeframe drives it home. “The consistency of this relationship is surprising because, on this timescale, we expect solar luminosity to influence climate,” the authors write. “We hypothesize that changes in planetary albedo and other greenhouse gases (e.g., methane) helped compensate for the increasing solar luminosity through time.”
Overall, Earth’s global mean surface temperature (GMST) ranged from 11° to 36°C during the Phanerozoic, a larger range than previously thought. It also shows that greenhouse climates were hotter than thought. The largest temperature swings were in the high latitudes, but tropical temperatures ranged from 22 C to 42 C. This goes against the idea that the tropics have a fixed upper limit and shows that life must have evolved to survive in those higher temperatures.
The research also shows that our current climate is actually cooler than the climate through most of the Phanerozoic. Technically, Earth is in an ice age right now, though the ice is receding and has been for thousands of years. Earth’s current GMST is 15 Celsius, lower than during most of the Phanerozoic.
But while that may sound comforting, it’s not. It’s the rate of change in the GMST that’s dangerous. Our GHG emissions are warming the planet faster than at any time during the Phanerozoic.
“Humans, and the species we share the planet with, are adapted to a cold climate,” Tierney said. “Rapidly putting us all into a warmer climate is a dangerous thing to do.”
This figure from the published research shows the climate states through the Phanerozoic. D shows the latitudinal surface air temperature gradient associated with each of the climate states. Coloured bands show the 16th to 84th percentiles, and coloured lines show the median value. Image Credit: Judd et al. 2024.
While PhanDA is generally in agreement with previous climate reconstructions, it deviates in some ways. For example, cold climate periods don’t always coincide with glaciation and ice ages. Earth’s surface is ever-changing, and that can make some conclusions difficult to reach. “Many of the traditional glacial indicators can have nonglacial origins, complicating the interpretation of the rock record, and limited outcrop of older rocks and poor age control can make it difficult to discern between isolated alpine glaciers and widespread ice sheets,” the authors explain.
But that doesn’t take much away from PhanDA. It strengthens our understanding of climate and carbon.
This figure illustrates the undeniable relationship between atmospheric carbon and a warming climate. B shows PhanDA GMST versus CO2, colour-coded by geologic era. The black dashed line shows the York regression, a statistical method used to draw a straight line between data points with some uncertainties. C shows the CO2 ranges for each of the defined climate states. Image Credit: Judd et al. 024.
Shockingly, the work suggests that Earth’s climate is even more sensitive to CO2 than some current models show.
“PhanDA GMST exhibits a strong relationship with atmospheric CO2 concentrations, demonstrating that CO2 has been the dominant force controlling global climate variations across the Phanerozoic,” the authors write in their conclusion.
If there really are advanced alien civilizations out there, you’d think they’d be easy to find. A truly powerful alien race would stride like gods among the cosmos, creating star-sized or galaxy-sized feats of engineering. So rather than analyzing exoplanet spectra or listening for faint radio messages, why not look for the remnants of celestial builds, something too large and unusual to occur naturally?
The most common idea is that aliens might build something akin to a Dyson sphere. In their need for more powerful energy sources, an advanced civilization might harness the entire output of a star. They wrap a star within a sphere to capture every last photon of stellar energy. Such an object would have a strange infrared or radio spectrum. An alien glow that is faint and unique. So astronomers have searched for Dyson spheres in the Milky Way, and have found some interesting candidates.
One major search was known as Project Hephaistos, which used data from Gaia, 2MASS, and WISE to look at five million candidate objects. From this they found seven unusual objects. They appear to be M-type red dwarfs at first glance, but have spectra that don’t resemble simple stars. This kind of star-like infrared object is exactly what you’d expect from a Dyson sphere. But of course extraordinary claims require extraordinary evidence, and that’s where things get fuzzy.
Almost immediately after the paper was published, other astronomers noted that the seven objects could also be hot Dust-Obscured Galaxies, or hotDOGs. These are quasars, so they appear star-like, but are obscured by such a tremendous amount of dust that they mostly emit in the infrared. And their spectra can be quite different from a M-type star. So the challenge is to distinguish between a hotDOG and a Dyson sphere. Which is where a new paper on the arXiv comes in.
Rather than trying to specifically distinguish between the two, the authors instead look at the distribution of known hotDOGS. They found that statistically about 1 in 3,000 quasars are of the hotDOG type, so that a broad search for Dyson spheres would likely include some dusty quasars. The authors go on to note that any civilization powerful enough to build star-scale structures would also have the ability to obscure their infrared signal. We can’t simply assume that aliens would build a Dyson sphere in such an obvious way. Overall, the authors argue, the seven candidate superstructures can be accounted for by hotDOGs and other phenomena, thus there is currently no clear evidence for alien superstructures.
