Not Just Water. Enceladus is Also Blasting Silica Into Space

Deep beneath the icy surface of Saturn’s moon Enceladus, something’s happening that causes particles of icy silica to spew out to space. They eventually end up in Saturn’s E ring. Planetary scientists knew that this was happening, but didn’t have a good explanation for why or how. Now, they do.

A new study done by a team at the University of California Los Angeles offers some answers. Their work shows that tidal heating in Enceladus’ rocky core creates currents (or flows) that transport the silica. Then, it’s probably released by deep-sea hydrothermal vents over the course of just a few months.

“Our research shows that these flows are strong enough to pick up materials from the seafloor and bring them to the ice shell that separates the ocean from the vacuum of space,” said Ashley Schoenfeld, a doctoral student at UCLA. “The tiger-stripe fractures that cut through the ice shell into this subsurface ocean can act as direct conduits for captured materials to be flung into space. Enceladus is giving us free samples of what’s hidden deep below.”

Why Enceladus Spews its Secrets

Data from the missions that visited the Saturn system keep revealing surprises about the Saturnian moons. We now know that Enceladus is an ocean world, for example. That’s because it has a large volume of liquid water mostly locked away beneath the icy surface. The surface itself is extremely reflective and has cracks that allow fountains of icy particles to escape into space. Those so-called “tiger stripes” provide an exit point for the icy silica.

Those particles start out on the sea floor deep beneath the surface. The tidal forces that squeeze Enceladus under the grip of Saturn’s strong gravity deform this little moon. That creates friction in the surface as well as the rocky core underneath the ocean. That sets up currents in the watery ocean.

A rendering of the sediment capture model developed in the UCLA-led study, showing buoyancy effects on silica grains produced at hydrothermal vents along the sea floor and how this eventually leads to their escape through cracks in the outer ice shell of Enceladus. Courtesy: Ashley Schoenfeld/UCLA; NASA/JPL.

Hydrothermal Activity Plays a Role Inside Enceladus

Although the Voyager mission first revealed the strange surface of Enceladus, it wasn’t until Cassini made its long-term studies that planetary scientists found the plumes jetting out from the tiger stripes. The spacecraft measured large amounts of hydrogen gas in those plumes. That’s pretty strong evidence of hydrothermal activity on the ocean floor.

Hydrothermal vents deep in Earth’s oceans. Could similar types of vents power the transport of silica and other materials out from Enceladus? Credit: NOAA

Hydrothermal heating on Earth happens near volcanically active places beneath the sea, particularly in mid-ocean ridges. Those are where tectonic plates are spreading apart. That action allows volcanic material to spew up from beneath and superheat the water. On Enceladus, the friction caused by tidal heating creates hotspots that feed the currents carrying silica particles to space.

The UCLA team led by Schoenfeld created a model to simulate that process. It also allowed them to estimate a timeframe for it. Their model also explains why the currents are transporting other materials to the surface in addition to the silica. “Our model provides further support to the idea that convective turbulence in the ocean efficiently transports vital nutrients from the seafloor to ice shell,” said second author Emily Hawkins, a UCLA alumna who is now an assistant professor of physics at Loyola Marymount University.

Of course, the presence of heat and water raises the question of whether Enceladus is hospitable to life. On Earth, hydrothermal vents support an amazing variety of life forms. It remains for future missions to Enceladus to pin that down. They could study places inside that moon to see if it could support life. Those efforts would require landers to gather more information both on the ice and deep in the subsurface ocean.

For More Information

UCLA-led study explains how one of Saturn’s moons ejects particles from oceans beneath its surface
Particle entrainment and rotating convection in Enceladus’ ocean

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Astronomers Suspected There Should Be a Planet Here, and Then They Took a Picture of it

To date, astronomers have confirmed 5,272 exoplanets in 3,943 systems using a variety of detection methods. Of these, 1,834 are Neptune-like, 1,636 are gas giants (Jupiter-sized or larger), 1,602 are rocky planets several times the size and mass of Earth (Super-Earths), and 195 have been Earth-like. With so many exoplanets available for study (and next-generation instruments optimized for the task), the process is shifting from discovery to characterization. And discoveries, which are happening regularly, are providing teasers of what astronomers will likely see in the near future.

For example, two international teams of astronomers independently discovered a gas giant several times the mass of Jupiter orbiting a Sun-like star about 87.5 light-years from Earth. In a series of new papers that appeared in Astronomy & Astrophysics, the teams report the detection of a Super-Jupiter orbiting AF Leporis (AF Lep b) using a combination of astrometry and direct imaging. The images they acquired using the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE) have since become the ESO’s Picture of the Week.

The groups were led by Dino Mesa, a researcher with the Osservatorio Astronomico di Padova and the Instituto Nazionale di Astrofisica (INAF), and Robert De Rosa, an astronomer with the European Southern Observatory’s (ESO) Paranal Observatory in Chile. Using data from the European Space Agency’s (ESA) Hipparcos and Gaia satellites, the teams confirmed the presence of AF Lep b using astrometric measurements.

Similar to the Radial Velocity Method, this method consists of monitoring the motion of stars for signs of gravitational perturbance – which indicate the presence of orbiting planets. When consulting data on AF Leporis, the teams noticed a slight wobble indicative of a massive planet in orbit around it. These were followed up with observations using the SPHERE on the ESO’s Very Large Telescope (VLT) using its suite of advanced instruments.

This includes adaptive optics that correct for the blurring caused by atmospheric interference and a coronagraph that blocks out the brightness of a star so that light reflected from the atmospheres and surfaces of orbiting planets can be seen. When applied to AF Leporis, the two teams observed a gas giant roughly two to five times the mass of Jupiter. This makes AF Lep b the lightest exoplanet detected with the combined use of astrometric measurements and direct imaging.

The AF Leporis system shares similar features to our Solar System. As an F-type main-sequence star, AF Leporis is roughly the same size, masa, and temperature as the Sun (a G-type main-sequence star). In addition, the planet orbits its parent star at a distance similar to that between Saturn and the Sun, and the system has a debris belt with similar characteristics as the Kuiper Belt. However, the star and its system are quite young (~24 million years), which means that future studies could provide new insight into how the Solar System formed.

Further Reading: ESO, Astronomy & Astrophysics (Feb 14), Astronomy & Astrophysics (Feb 21)

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59 New Planets Discovered in Our Neighborhood

The hunt for habitable extrasolar planets continues! Thanks to dedicated missions like Kepler, TESS, and Hubble, the number of confirmed extrasolar planets has exploded in the past fifteen years (with 5,272 confirmed and counting!). At the same time, next-generation telescopes, spectrometers, and advanced imaging techniques are allowing astronomers to study exoplanet atmospheres more closely. In short, the field is shifting from the process of discovery to characterization, allowing astronomers to more tightly constraint habitability.

Finding potentially-habitable “Earth-like” planets around these fainter stars is the purpose of the Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrographs (CARMENES), located at the Calar Alto Observatory in Spain. In a study that appeared in Astronomy & Astrophysics today, the CARMENES Consortium published data (Data Release 1) data from about 20,000 observations taken between 2016 and 2020. Among the measurements obtained from 362 nearby cool stars, the DR1 contained data on 59 new planets.

The CARMENES instrument is an optical and near-infrared spectrograph mounted on the 3.5-meter telescope and one of the most sophisticated planet-hunting in the world using the Radial Velocity Method. Also known as Doppler Spectroscopy, this method consists of measuring light from distant stars with spectrometers to look for signs of redshift and blueshift – which show if the planet is moving back and forth. This movement indicates the presence of gravitational forces acting on the star (i.e., a system of orbiting planets) and can yield accurate mass estimates.

Illustration of the CARMENES planets. All planets discovered with the same method as CARMENES, but with other instruments, are shown as grey dots. © Institut d’Estudis Espacials de Catalunya (IEEC)

The CARMENES Consortium that designed and built this instrument includes more than 200 scientists and engineers from 11 Spanish and German institutions. This includes the Max-Planck-Institut für Astronomie (MPIA), the Institut d’Estudis Espacials de Catalunya (IEEC), the Instituto de Astrofísica de Andalucía (IAA-CSIC), the Instituto de Astrofísica de Andalucía (IAA-CSIC), the Institut de Ciències de l’Espai (ICE-CSIC), the Institut für Astrophysik Göttingen (IAG), the Instituto de Astrofísica de Canarias (IAC), the Centro de Astrobiología (CAB, CSIC-INTA) and the Centro Astronómico Hispano-Alemán (CAHA).

As of 2015, the Consortium’s purpose has been to look for terrestrial-type exoplanets around nearby red dwarf stars. Since then, the CARMENES instrument has doubled the number of known exoplanets around nearby M-type stars using the Radial Velocity Method. The 59 exoplanets they identified between 2016 and 2019 are either new discoveries or confirmations of previously-detected candidates, including 6 Jupiter-like gas giants, 10 Neptune-like gas giants, and 43 Earths and Super-Earths. A dozen of these latter planets were found to orbit within the stars’ circumsolar habitable zones.

“Since it came into operation, CARMENES has re-analyzed 17 known planets and has discovered and confirmed 59 new planets around stars in the vicinity of our Solar System, making a significant contribution to expanding the census of nearby exoplanets,” said Dr. Ignasi Ribas, a researcher at the ICE-CSIC and Director of the Institute of Space Studies of Catalonia (IEEC) who led the stud, in a recent MPIA press release.

“In order to determine the existence of planets around a star, we observe it a minimum of 50 times,” added Juan Carlos Morales, an IEEC researcher at ICE-CSIC. “Although the first round of data have already been published to grant access to the scientific community, the observations are still ongoing.”

Artist’s conception of a rocky Earth-mass exoplanet like Wolf 1069 b orbiting a red dwarf star. Credit: NASA/Ames Research Center/Daniel Rutter

The paper published in Astronomy & Astrophysics is the 100th study produced by the CARMENES Consortium, demonstrating the project’s success in detecting exoplanets around fainter, low-mass stars. Between 2016 and 2019, CARMENES observed almost half of all nearby M-type stars in two near-infrared wavelength ranges – 0.52 to 0.96 µm and 0.96 to 1.71 µm – some of which can only be observed from the Southern Hemisphere. In addition, the spectra they obtained provided information about the atmospheres of the stars and their planets, which is essential to characterization.

The Consortium team hopes that the publication of this first large dataset will stimulate further research and discoveries. Experts are also using the visible light data from the stars surveyed to improve CARMENE’s infrared data processing. Once that information becomes public, astronomers will have another large dataset of observations to work with. In the meantime, the Consortium is conducting more observations of the same stars through CARMENES Legacy-Plus, which began in 2021 and is expected to last until the end of 2023.

The CARMENES Consortium plans to survey about 300 late-type main-sequence stars M5V stars – red dwarf suns roughly 0.162 times as massive as the Sun. The ultimate goal is to detect up to 2 million Earth-like planets that orbit within the habitable zones of M-type stars. This will go a long toward settling the debate about whether or not life can survive under “crimson skies,” which remains the subject of considerable debate.

Further Reading: MPIA, Astronomy & Astrophysics

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Europa Could be Covered in Salty Ice

Jupiter’s second Galilean moon, Europa, is one of the most fascinating planetary objects in our Solar System with its massive subsurface ocean that’s hypothesized to contain almost three times the volume of water as the entire Earth, which opens the possibility for life to potentially exist on this small moon. But while Europa’s interior ocean could potentially be habitable for life, its unique surface features equally draw intrigue from scientists, specifically the large red streaks that crisscross its cracked surface.

While these red streaks are one of the most striking features on Europa, scientists have been unable to identify its chemical signature since no substance on Earth possesses a complementary signature itself. They have previously made their own hypotheses to their origins, with a 2015 study suggesting the red streaks could come from Europa’s interior ocean sea salt that has been blasted with radiation on the surface.

It is these red streaks, and more specifically their chemical origin, that an international team of researchers led by the University of Washington (UW) have addressed in a recent study with the discovery of a new kind of solid crystal that could help explain the scientific processes responsible for the red streaks’ existence on Europa. While this new crystal was created in a laboratory setting, scientists hypothesize it could also form at the bottom of the deep oceans on worlds like Europa, as well. The newly discovered solid crystal is formed from water and table salt (sodium chloride), which are two of the most common substances found on Earth.

Learn more about this remarkable study here!

“It’s rare nowadays to have fundamental discoveries in science,” said Dr. Baptiste Journaux, who is an acting assistant professor in UW’s Department of Earth and Space Sciences, and lead author of the study. “Salt and water are very well known at Earth conditions. But beyond that, we’re totally in the dark. And now we have these planetary objects that probably have compounds that are very familiar to us, but at very exotic conditions. We have to redo all the fundamental mineralogical science that people did in the 1800s, but at high pressure and low temperature. It is an exciting time.”

For the study, the researchers investigated what is known as a hydrate, which is an icy lattice formed in cold water temperatures from the combination of salts and water. Until now, only one sodium chloride hydrate was known to exist, known as hydrohalite, which consists of one salt molecule for every two water molecules.

Using transparent diamonds and cold temperatures, the team compressed a miniscule amount of salty water near 25,000 times Earth’s atmospheric pressure, where they observed two new sodium chloride hydrate crystal structures. The first structure contains two sodium chloride molecules for every 17 water molecules, and the other contains one sodium chloride molecule for every 13 water molecules. It was also discovered that the structure containing 17 water molecules remained stable even near vacuum pressure, which is equivalent to the Moon’s surface, while the structure containing 13 water molecules only maintained its stability at high pressure. It is hypothesized that these unique crystal structures could help explain the “watery” signatures from Jupiter’s moons.

This microscopic image displays the study’s newly discovered hydrate containing two sodium chloride molecules for every 17 water molecules. This crystal structure was produced at high pressure but maintains its stability under cold and low-pressure environmental conditions. Scale bar: 50 micrometers = 0.000050 meters. (Credit: Journaux et al./PNAS)

Previously known sodium chloride hydrate containing one salt molecule for every two water molecules (left); two newly discovered crystal structures with two sodium chloride molecules for every 17 water molecules (center) and one sodium chloride molecule for every 13 water molecules (right). (Credit: Baptiste Journaux/University of Washington)

“We were trying to measure how adding salt would change the amount of ice we could get, since salt acts as an antifreeze,” said Dr. Journaux. “Surprisingly, when we put the pressure on, what we saw is that these crystals that we were not expecting started growing. It was a very serendipitous discovery.”

These same cold, high-pressure environments likely exist on Europa, as scientists postulate its interior ocean could be hundreds of kilometers deep underneath approximately 5 to 10 kilometers of ice, with denser ice structures possibly existing at the bottom of the ocean where the temperatures and pressures would be even colder and more extreme.

For next steps, the researchers wish to create or collect a bigger sample to conduct a more in-depth investigation regarding whether icy moons signatures such as the red streaks found on Europa complement the two recently discovered hydrates.

Both NASA and the European Space Agency (ESA) currently have a few planetary missions scheduled to visit Europa and Titan to explore their potential habitability. These include the ESA’s Jupiter Icy Moons Explorer, also known as JUICE, which is slated to launch in April of this year and arrive at the Jupiter system in July 2031; NASA’s Europa Clipper mission, which is slated to launch in October 2024 and arrive at the Jupiter system in 2030; and NASA’s Dragonfly mission to Titan, which is slated to launch in 2027 and arrive at Titan in 2034. All these missions will attempt to learn more about the chemical compositions of these mysterious and intriguing worlds, which will help scientists determine the best ways to search for life.

Get a recent update on NASA’s Europa Clipper mission here!

“These are the only planetary bodies, other than Earth, where liquid water is stable at geological timescales, which is crucial for the emergence and development of life,” said Dr. Journaux. “They are, in my opinion, the best place in our solar system to discover extraterrestrial life, so we need to study their exotic oceans and interiors to better understand how they formed, evolved and can retain liquid water in cold regions of the solar system, so far away from the sun.”

What new discoveries will scientists make about Europa, its chemical signatures, and potential for life in the coming years and decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!

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Recreating the Extreme Forces of an Asteroid Impact in the Lab

About 50,000 years ago, a nickel-iron meteorite some 50 meters across plowed into the Pleistocene-era grasslands of what is now Northern Arizona. It was traveling fast—about 13 kilometers per second. In just a few seconds, an impact dug out a crater just over a kilometer wide and spread rocks from the site for miles around.

For years, scientists have worked to understand all the forces at work in such an impact event like the one that carved out Meteor Crater. Clearly, impacts have huge effects. The aftermath of the collision affects the landscape and leaves behind a scene of destruction. Yet, as often as Earth has been hit, obvious craters like the one in Arizona are relatively rare. That’s because erosion, weathering, and plate tectonics erase them over geologic time. Unless you know exactly where to look, you might not be able to find obvious evidence that something smacked into our planet.

The Clearwater East & West impact craters in Quebec, Canada (image credit: Google Earth). These forms are still visible, even though they are filled with water. Other craters on Earth, such as the Chixculub site in Mexico, are harder to identify.

So, how to understand the forces at work in an impact? According to Professor Falko Langenhorst from the University of Jena, scientists need to study the indirect effects of impacts. These include precision examination of shocked minerals and impact glass—often referred to as lamellar structures. When something hits the ground with tremendous force, it affects materials down to the crystalline level of minerals. These lamellar structures are best studied using electron microscope techniques.

Finding Evidence of Shocked Grains

“For more than 60 years, these lamellar structures have served as an indicator of an asteroid impact, but no one knew until now how this structure was formed in the first place,” Liermann said, discussing a set of techniques that allowed them to study these shocked grains. “We have now solved this decades-old mystery.”

Langenhorst’s team came up with a way to simulate the incredible forces of an asteroid impact in the lab. The idea was to put quartz crystals (similar to the rocks shocked by the Meteor Crater event) under extremely high pressure inside a laboratory instrument. They used something called a “dynamic diamond anvil cell” (dDAC). It allows the science team to control pressures inside and change them very quickly. This simulates the rapidly changing pressures and temperatures at work during an actual impact event.

The impact simulated at the Jena lab creates tiny glass lamellae in quartz crystald. These structures are only tens of nanometers wide, so they had to be studied using an electron microscope. Courtesy: Falko Langenhorst, Christoph Otzen (University of Jena).

With this device, the scientists compressed single, tiny quartz crystals, putting them under tremendous pressure. At the same time, they shone an intense X-ray light through the crystals. This allowed them to witness changes to the crystal structure. “The trick is to let the simulated asteroid impact proceed slowly enough to be able to follow it with the X-ray light, but not too slowly, so that the effects typical of an asteroid impact can still occur,” Liermann said.

Looking at an Impact Second-by-Second

Experiments on a scale of seconds proved to be the right duration. This roughly simulates just how quickly an impactor can affect the landscape it’s encountering. Essentially, it transforms a quiet grassland into a rapidly expanding upheaval, melting rock and turning the surface into a hole in an extremely short period of time. The experiment in Jena focused on the split-second actions of the impact.

“We observed that at a pressure of about 180,000 atmospheres, the quartz structure suddenly transformed into a more tightly packed transition structure, which we call rosiaite-like,” reported team member Christoph Otzen, who is writing his doctoral thesis on these studies. (Technically, rosiaite is an oxidic mineral and the namesake for the crystal structure that is known from various materials. It does not consist of silica, but is a lead antimonate (a compound of lead, antimony, and oxygen).)

“In this crystal structure, the quartz shrinks by a third of its volume. The characteristic lamellae form exactly where the quartz changes into this so-called metastable phase, which no one has been able to identify in quartz before us,” said Otzen.

Looking Beyond Impacts

Understanding asteroid impacts on our planet (and others), gives a lot of insight into the interaction between these space rocks and planetary surfaces. After all, impact events shaped our worlds—starting from the first collisions of planetesimals in the early solar system. Earth has been hit many times and is not yet free from the dangers of impacts. So, it’s important to understand the intricate forces at work when something from space smacks into our planet.

However, the Jena team’s study has implications beyond the study of cratering events, according to Langenhorst. “What we observed could be a model study for the formation of glass in completely different materials such as ice,” Langenhorst pointed out. “It might be the generic path that a crystal structure transforms into a metastable phase in an intermediate step during rapid compression, which then transforms into the disordered glass structure. We plan to investigate this further because it could be of great importance for materials research.”

For More Information

Asteroid Impact in Slow Motion
Evidence for a rosiaite-structured high-pressure silica phase and its relation to lamellar amorphization in quartz

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It Should be Possible to Farm on the Moon

An astronaut’s gotta eat, right? Especially if they are on a long-duration mission to places like the Moon. Scientists have been looking into how the lunar regolith could possibly support growing food for humans, as growing plants for food and oxygen will be critical for future long-term lunar missions.

One company has been diligently researching this concept and they say there’s good news.

By analyzing lunar samples returned by the Apollo astronauts and China’s Chang’e 5 mission, scientists at Solsys Mining in Norway says that many valuable plant nutrients already exist in the lunar regolith. The company says they are now developing systems for extracting these nutrients for use in hydroponic agriculture.

Their concept is to use those in-situ nutrients to create fertilizer for aquacultural farming. Solsys has also developed 3d-printed hydroponic growth systems.

“This work is essential for future long-term lunar exploration,” said ESA materials and processes engineer Malgorzata Holynska, who has been working with various industries on promising new ideas in space research. “Achieving a sustainable presence on the Moon will involve using local resources and gaining access to nutrients present in lunar regolith with the potential to help cultivate plants. The current study represents a proof of principle using available lunar regolith simulants, opening the way to more detailed research in future.”

The dusty, sandy pebbly soil is known as the lunar regolith. That’s Neil Armstrong’s boot on the Moon. Credit: NASA

Hydroponics appears to be the best and maybe only option for growing food on the Moon. Solsys says their research has revealed that lunar soil compacts in the presence of water, which creates problems for plant germination and root growth.

Hydroponics, the technique of growing plants using a water-based nutrient solution rather than soil, therefore offers a practical alternative for lunar farming. Extracting nutrients from the regolith allows for in-situ resource utilization, meaning that fertilizer wouldn’t have to be hauled to the Moon, which would be expensive.

In their research, the Solsys Mining team having already cultivated beans by extracting nutrients from a simulated lunar highland regolith.

“We are developing systems for beneficiation of raw materials to enable agriculture, construction and production in space,” says the company on their website. “Systems in space need to be gravity independent, dry, highly energy efficient, compact, and use little to no water.”

Artist concept of a future farm on the Moon. Credit: Solsys Mining.

Their concept for the whole system, shown in this artist rendition, includes a mechanical sorting area for the regolith, on the left, which would then pass through to the central module for more advanced processing, such as chemical leaching. Finally extracted nutrients would be dissolved in water to be pumped to the hydroponic garden, shown on the right.

While the hydroponic bays have been developed, the company is working on the technologies needed for screening, sorting and extracting the nutrients. Solsys Mining’s founders have experience from both the terrestrial mining sector and the space industry.

All of these systems would need to be able to operate in the Moon’s challenging environment, which includes reduced gravity, no atmosphere, and extremes in radiation and temperatures. Working with the lunar regolith itself poses challenges as it is very abrasive and can cause a range of problems for both astronauts and equipment. Since its abrasive nature can damage machines, mechanical durability would need to be built into the system.

This concept has received support from ESA’s Open Space Innovation Platform, which looks for promising new ideas for space research.

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How are Mars Rocks Getting “Shocked” by Meteorite Impacts?

On Mars, NASA’s Perseverance rover is busy collecting rock samples that will be retrieved and brought back to Earth by the Mars Sample Return (MSR) mission. This will be the first sample-return mission from Mars, allowing scientists to analyze Martian rocks directly using instruments and equipment too large and cumbersome to send to Mars. To this end, scientists want to ensure that Perseverance collects samples that satisfy two major science goals – searching for signs of life (“biosignatures”) and geologic dating.

To ensure they select the right samples, scientists must understand how rock samples formed and how they might have been altered over time. According to a new NASA study, Martian rocks may have been “shocked” by meteorite impacts during its early history (the Late Heavy Bombardment period). The role these shocks played in shaping Martian rocks could provide fresh insights into the planet’s geological history, which could prove invaluable in the search for evidence of past life on Mars.

The study was led by Dr. Svetlana Shkolyar, a planetary scientist at NASA’s Goddard Space Flight Center and the Blue Marble Space Institute of Science (BMSIS). She was joined by researchers from the American Museum of Natural History (AMNH), the John Hopkins University Applied Physics Laboratory (JHUAPL), the Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie (IMPMC), the University of the Basque Country, the Los Alamos National Laboratory, the Niels Bohr Institute, NASA Goddard, and the NASA Jet Propulsion Lab.

This annotated image from NASA’s Perseverance Mars rover shows its wheel tracks in Jezero Crater and a distant view of the first potential location it could deposit a group of sample tubes for possible future return to Earth. Credits: NASA/JPL-Caltech

Their study, published in the journal Earth, Moon, and Planets, described how samples of Martian feldspar collected by Perseverance could be characterized by its SuperCam and Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC) instruments. As Shkolyar explained in a recent NASA press release:

“Because we’re counting on these samples to reveal a record of Mars’ geologic past, it would be important for us to understand if and how the rocks have been altered. The heat and pressure of an impact event can cause the rocks affected by it to melt. This means that when we study these rocks today, millions or even billions of years after the impacts occurred, the rocks could have had their original characteristics altered. It could even make one type of rock look like a different type of rock altogether.”

Shkolyar and her team focused on a type of rock mineral common to Earth and Mars: plagioclase feldspar. Feldspar refers to a group of rock-forming aluminum minerals containing positively-charged elements (sodium, calcium, potassium, or barium) and making up about 75% of Earth’s crust. Plagioclase minerals are the most common members of this group and are produced during the weathering of igneous and metamorphic rocks. Their study details how impact shocks can be identified in plagioclase and how improved instrumental methods can characterize the chemistry of rocks.

According to Shkolyar, this will come in handy when the cache of samples is returned to Earth. The study of impact-shocked samples could help scientists more precisely define when the Late Heavy Bombardment occurred and how long it lasted. This period occurred during the early Solar System (between 4.1 to 3.8 billion years ago) when the planets were in less-stable orbits and subjected to frequent asteroid impacts. These impacts are believed to have played a vital role in the distribution of water throughout the Solar System (and the building blocks of life).

Shkolyar and her team emphasize that there are important considerations when selecting samples. This included documenting the environmental context of samples before they are collected and cached. Said Shkolyar:

“For both astrobiology and dating the age of the rocks, the effect of impact shock is very important to consider. When looking for fossil carbon in these rocks, which could be an indicator of past life, the alterations imposed by impact shock could alter the carbon signature. An example of how shocked samples could be beneficial would be to help us understand the history of impact on Mars. Impact-shocked samples would contain geologic indicators which would help us to constrain the duration of the Heavy Bombardment more accurately.”

The Sample Return Mission is a cooperative program between NASA and the European Space Agency (ESA). This mission will consist of four major elements that will commence launching in 2026, starting with a Sample Retrieval Lander (provided by NASA) that will touch down on the surface. Perseverance will deliver the samples to the lander with the assistance of two Sample Recovery Helicopters (NASA) similar to Ingenuity. The Mars Ascent Vehicle (NASA) will launch the samples into orbit, where they’ll be retrieved by the ESA’s Earth Return Orbiter and transported back to Earth.

This will allow for studies that are far more detailed than any performed previously by robotic missions. The results will help scientists gain a better understanding of Mars’s past and subsequent evolution, especially where the possible existence of life is concerned. By dating rocks and inferring the chronology of Mars, scientists can determine how long Mars had habitable conditions on its surface. With any luck, the analysis will also show indications of past life and maybe even point to where we might find it today.

Further Reading: NASA

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