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Astrochemistry

3 rovers will head to Mars in 2020. Here’s what you need to know about their chemical missions

For the first time, China, Europe, Russia, and the US could have vehicles on the Red Planet operating simultaneously

by Sam Lemonick
July 21, 2019 | APPEARED IN VOLUME 97, ISSUE 29

Credit: NASA/JPL-Caltech/MSSS/JHU-APL | The Mars 2020 rover will explore an ancient delta in Jezero crater, shown in this colorized image.

 

In brief

Three rovers will launch to Mars in 2020 aiming for different landing sites. The US mission, the Chinese mission, and a joint European-Russian mission will all pack chemical and geological instruments on their rovers to answer questions about Mars’s past habitability and whether life ever existed there. The European rover will drill for samples 2 m below Mars’s surface for the first time. NASA’s rover will collect and store samples to be returned to Earth at a later date for advanced analysis. It will also test an instrument that could aid future exploration by humans on the Red Planet. China’s would be the country’s first successful Mars mission. If the rovers make it, scientists expect to gain new insight into Mars’s history. Read on about the rovers, where they’re headed, and what they might discover.

Mars reaches its closest point to Earth every 26 months. If you want to send a spacecraft to the Red Planet, that’s the time to do it. And that’s exactly what the US, Europe, Russia, and China plan to do next year.

Three missions are scheduled to blast off in July 2020: NASA’s Mars 2020; ExoMars 2020, run jointly by the European Space Agency (ESA) and Russia’s Roscosmos; and the Mars 2020 mission of the China National Space Administration (CNSA). The first mission aims to, for the first time, collect martian samples that will one day be returned to Earth. The second plans to drill deeper than ever before beneath Mars’s surface, where signs of life may lie waiting. The third would be China’s first successful Mars landing.

Like most Mars rovers, all three carry instruments that can analyze molecules in rocks and soil to look for evidence that life existed—or exists—on the Red Planet. NASA’s mission will also test equipment that could be used in a future mission in which humans travel to Mars. If all three rovers land successfully and are able to return data to scientists on Earth, they will be the 9th, 10th, and 11th spacecraft to do so.

“There’s still so much we have to explore,” says Kirsten Siebach, a geologist studying Mars at Rice University.

Sticking the landing

The trip to Mars takes about 7–10 months. After escaping Earth’s gravity, each spacecraft will keep moving outward from the sun until it intercepts Mars. While the launch and the long journey pose their own dangers—several past missions have failed during these stages—the real trick to putting a rover on Mars is sticking the landing.

A spacecraft is traveling about 20,000 km/h, 10 times as fast as a speeding bullet, when it hits Mars’s atmosphere. Although the atmosphere is thin, it still contains air molecules that cause friction. A heat shield protects the spacecraft as it plunges through these molecules toward the surface. And a specially designed parachute or parachutes deploy to slow the spacecraft to hundreds of kilometers per hour as it continues to plummet toward Mars. Rockets then fire to slow the craft further.

All of this takes about 7 minutes. But because 14 minutes are required for a signal to travel between Earth and Mars, NASA calls these 7 minutes the “7 minutes of terror,” during which scientists don’t know if the spacecraft has made it safely. The time delay also means a craft has to find its way to the surface without human control.

After the rockets fire, the three missions will diverge in terms of how they’ll get their craft to the ground. The CNSA will inflate airbags to cushion its craft’s impact, according to news reports. These will deflate after the landing, allowing HX-1 (aka the Mars Global Remote Sensing Orbiter and Small Rover) to deploy. NASA’s previous Spirit and Opportunity Mars rovers used this method in 2004. Roscosmos will fire its Kazachok landing platform’s rockets until it is within a few meters of the surface. The Rosalind Franklin rover should then land softly on shock-absorbing legs. The previous ESA-Roscosmos mission to Mars, in 2016, used a similar Russian lander called Schiaparelli, which crashed into the planet at more than 500 km/h because of a combination of hardware and computer problems.

For NASA’s as-yet-unnamed 2020 rover, it will use a “sky crane” system like the one it used in 2012 to land the Curiosity rover, which is still operating on Mars. About 20 m from the surface, the lander will lower the rover softly onto the ground on cables, then detach and fly away to crash-land at a safe distance. The NASA spacecraft will use new technology to pick a safe landing site. Onboard cameras and computers will compare the surface with stored photographic maps of Mars, and the craft should be able to change its landing site on the fly if it’s headed for dangerous obstacles.


Rovers at a glance

The three rovers scheduled to explore Mars in 2021 will carry some similar instruments and some unique ones.


On the surface

One of Earth’s defining features is its geological activity. Plate tectonics, volcanoes, and liquid water have shaped and reshaped our planet over its history. Mars is much less active, but scientists are confident it had some or all of those features in its past. Those types of ancient geological activity, combined with meteorite impacts, have produced a diversity of features on the Red Planet, including mountains, lake beds, river valleys, and deltas. This gives the rovers plenty to explore.

“What you want to do, but you can’t afford, is send up many, many rovers to many parts of the planet,” says Raymond E. Arvidson, a geologist at the University of Washington in St. Louis. The next best thing, he says, is to pick diverse landing sites for a few missions to explore.

The mission is about chemistry.
Jorge Vago, ExoMars 2020 project scientist, European Space Agency

Spirit found evidence of a hot spring or volcanic vent in a crater on Mars. Opportunity found minerals that form where water flows on an open plain. Curiosity landed in another crater, called Gale crater, which is thought to have once held a shallow lake that evaporated over time, leaving sedimentary rocks and other minerals behind.

NASA’s Mars 2020 rover—which will be named in a contest later this year—is going to land in Jezero crater, whose main attraction is an ancient delta where a river once flowed into a large lake or sea. Timothy A. Goudge, a geologist at the University of Texas at Austin, says the new landing technology on the Mars 2020 craft is what enables us to explore this site, which was discovered only in 2005. “Jezero was actually in the running for the landing site for Curiosity” in 2012, he says, but it didn’t make the cut because the chance of safe landing was too low back then.

Goudge, who advocated for Jezero during NASA’s 2020 landing-site selection process, says the site has a number of geological features to explore. The delta would have collected water and sediment from a watershed of 30,000 km2, he says. That makes it a good place to look for signs of life. “Deltas are good collectors of organic matter on Earth,” so it’s reasonable to think they’d collect organic molecules on Mars, Goudge says. Jezero’s watershed is also thought to contain sediment washed downstream from some of the oldest martian crust.

Goudge notes that Mars orbiters—spacecraft that circle the Red Planet rather than land on it—have detected outcroppings of carbonate minerals in Jezero from afar. Scientists think it’s likely that atmospheric carbon dioxide created a greenhouse effect that transformed Mars from a wet planet to the dry one we see today. That CO2 should be stored in these carbonate minerals, but rovers haven’t found the physical evidence to back up the theory. NASA’s Mars 2020 mission may change that and answer questions about the history of the planet’s geology and atmosphere.

“We’re hoping to see something really fundamentally different than we’ve been able to see from orbit or from the collection of Mars meteorites,” says Kenneth A. Farley, a geochemist at the California Institute of Technology who’s the project scientist for NASA’s Mars 2020 mission.

China hasn’t announced where its rover will land, but the European and Russian ExoMars mission is shooting for a plain called Oxia Planum. Similar to Jezero crater, Oxia Planum is thought to hold clay deposits left over from an ancient body of water that flowed out of several waterways. The site is at the outflow of one of the largest systems of ancient waterways on Mars, according to Jorge Vago, the project scientist at ESA for the ExoMars 2020 mission. One thing that makes Oxia Planum especially interesting to Vago is that the body of water may have been very large, even an ocean. The past existence of a northern martian ocean still remains to be proven, but Vago thinks the ExoMars rover, named Rosalind Franklin, could help make the case.

But for all the interesting geology at the site, Vago says this mission’s focus will be chemistry. “The mission is not about geology, not about minerals. The mission is about chemistry.” Specifically, chemical evidence of life.


Credits: NASA/JPL-Caltech/University of Arizona (Viking model); NASA/JPL-Caltech/University of Arizona (Viking model); NASA/JPL (Viking sampling, Sojourner, Phoenix artist rendering); NASA/JPL/Cornell University (Spirit & Opportunity artist rendering); NASA/JPL-Caltech/MSSS (Curiosity); NASA/JPL-Caltech (Insight artist rendering, Mars 2020 artist rendering); ESA/ATG Medialab (Rosalind Franklin artist rendering); Xinhua via Getty Images (HX-1 artist rendering); USGS Astrogeology Science Center (landing sites)

09729-cover-sites.jpg
Credit: USGS Astrogeology Science Center
The landers and rovers that have successfully touched down on Mars have done so in regions scattered across the planet’s surface.
Note: Sites for Rosalind Franklin and Mars 2020 are proposed. HX-1 landing site not yet known.

Drilling in

The Rosalind Franklin rover will search for biosignatures, a term for a host of signs that life may have existed on Mars. These signs include fossils of cells, mineral structures associated with organisms, chemicals found in living creatures, and molecules modified by biological processes. “The biosignatures that carry the most weight are chemical ones,” Vago says.

The surface of Mars is not a friendly place for organic molecules. Earth’s atmosphere and magnetic field shield molecules on our planet from harmful solar and cosmic radiation. Mars has little of either protection. Past missions to Mars haven’t found many complex organic molecules in the regions of Mars’s surface that they’ve explored. That is why Rosalind Franklin will be looking elsewhere.

One of its key instruments is a drill capable of collecting samples from 2 m underground. The idea is to unearth samples that have been shielded from both radiation and oxidizing chemicals like perchlorates in Mars’s atmosphere, says François Raulin, an emeritus professor at University Paris-Est Créteil Val de Marne and coleader of the team that designed the Mars Organic Molecule Analyzer (MOMA), which will analyze drilled samples.

Whether the drill can work as planned remains to be seen. NASA’s InSight lander, which touched down on Mars in 2018 and is still in operation, also has a drill meant to dig as deep as 5 m. But it has a different design. It got about 30 cm down before it stopped moving, possibly because it ran into a rock. Scientists and engineers are still trying to figure out what to do next.

MOMA will carry out the ExoMars 2020 mission’s chemical analysis. It can use its ovens or lasers to volatilize molecules in samples that are brought up by the drill, then analyze those with gas chromatography/mass spectrometry and laser desorption mass spectrometry. The GC/MS and LD-MS instruments share a single linear ion trap to carry out the analysis. It was selected for its small size and ability to operate at ambient Mars pressure rather than under high vacuum. MOMA also carries reagents that can be added to samples to volatilize chiral molecules, small molecules like amino acids, and very large molecules intact.

The whole MOMA package is a collaboration between French, German, and US scientists. Raulin’s team contributed the gas chromatograph, the German team the laser desorption apparatus, and the US team the mass spectrometer and vacuum pump. But Fred Goesmann, MOMA’s principal investigator and a scientist at the Max Planck Institute for Solar System Research, says the different groups don’t think of the instruments as separate. The researchers designed MOMA “so that it couldn’t be split up,” he says.

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Still, using MOMA’s data to make conclusions about life on Mars won’t be simple. “Even proving there’s life here on Earth in a chemical way is by no means easy,” Goesmann says. Members of the MOMA team have been practicing on terrestrial rocks, and he says, “It’s hellishly difficult to tell if a carbon-bearing molecule is biotic or abiotic.” So the team will look for what he describes as a chain of evidence. One piece of evidence is chiral molecules. “If we find on Mars a pure enantiomer, this is a very good indication of the presence of life,” Raulin says. That’s because biology, at least on Earth, favors one enantiomer over the other of a given molecule. This is true for DNA and for amino acids. In addition to chirality, evidence could come in the form of molecular chain length. Goesmann points out that biology tends to add two carbons at a time when synthesizing compounds, so seeing a pattern of even- or odd-length molecules could be a biosignature.

MOMA is the last instrument in a chain of them that starts with the drill. The first instrument is the Mars Multispectral Imager for Subsurface Studies (Ma_MISS). This spectrometer collects data from a window a few millimeters wide on the side of the drill bit. Maria Cristina De Sanctis of the Italian National Institute for Astrophysics, the leader of the team in charge of Ma_MISS, says it will help guide sample collection—for instance, by identifying minerals that might be related to organic molecules. And she says if MOMA does detect organic molecules, Ma_MISS will be able to provide context for where they came from, which could help draw conclusions about whether they came from an organism.

After analysis by Ma_MISS but before MOMA, samples are analyzed by an infrared spectrometer, which will be used to determine minerals’ composition and origin, and a Raman spectrometer. Raulin says Raman spectra are a good place to look for organic molecules. “If we clearly see organics from IR and Raman, we know there is some important stuff” in the sample, he says.

Vago is certain Rosalind Franklin will find organic molecules. He says the chances of finding something suggestive of life, though, is about 50-50. “Remember, we’re talking about something that may have been alive 4 billion years ago,” he says. On Earth, something that age would be too degraded to detect, Vago adds, but Mars’s cold, preserving temperatures and more recent geological quiescence mean scientists might get lucky.

The fact there are three rovers headed to Mars is amazing.
Roger Wiens, SuperCam team leader, Los Alamos National Laboratory
09729-cover-wheelscxd.jpg
Credit: NASA/JPL-Caltech
Engineers at NASA’s Jet Propulsion Laboratory install legs and wheels on the Mars 2020 rover.

Sample return

NASA’s rover will also look for signs of past life but not in the same way. The University of Washington in St. Louis’s Arvidson describes an arc of Mars exploration that began in the 1970s with the Viking landers, which he worked on. Those landers took soil samples in the hopes of finding microbes. Arvidson says enthusiasm for Mars exploration in the US fell off quickly when it became clear there was no evidence of biological activity in the soil. The orbiting Mars Global Surveyor in the 1990s sparked new interest in studying martian geology, and the next rovers, Spirit and Opportunity, were essentially doing robotic field geology. Curiosity’s mission looked at the role water played on Mars and has evolved to explore the planet’s past habitability. All these missions carried the analytical equipment on board to answer those questions on-site. NASA’s Mars 2020 mission will be different.

“We think we know enough about the planet now” to collect samples but then return them to Earth for analysis, Arvidson says.

The idea is that scientists can analyze martian samples in ways that rovers can’t. “We can do an amazing amount with our rovers on Mars, but there are some things that we can’t do with a robot on Mars,” Rice University’s Siebach says.

She also points out that returned samples would continue to be available for decades on Earth, allowing new analysis as equipment improves or as new questions arise. “We’re still learning things from Apollo samples” collected on the moon, Siebach says.

In addition to performing some experiments similar to other Mars missions, NASA’s Mars 2020 rover will collect at least 20 pencil-sized cores drilled from martian rocks, seal them in tubes, and store them. What comes next is still only a guess, but scientists are confident that NASA will fund a mission to retrieve those samples. NASA administrator Jim Bridenstine said this year that the agency is committed to a sample-return mission, and the US House of Representatives approved a bill to fund ongoing research about how, exactly, NASA will do that.

One proposal, in collaboration with ESA, would send an additional lander to Mars, with a small rover to retrieve the cached samples and a rocket to propel them into Mars orbit. There, the samples would be transferred to an orbiter that could return them to Earth. NASA scientists had talked about launching those missions in the late 2020s, but Michael Meyer, NASA’s lead scientist for Mars exploration, said at a Mars exploration meeting this spring that budget constraints make a 2031 launch more realistic.

And if the return mission never happens, or it fails to bring the samples back? “If for some reason we never collect those, the mission is by no means a bust,” Arvidson says. The data collected by the experiments carried out on Mars’s surface would nevertheless add to our understanding of Mars.

Like Rosalind Franklin, NASA’s Mars 2020 rover will carry several instruments to help it search for suitable places to collect samples and provide context about them. The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals instrument, or SHERLOC, has a deep-ultraviolet Raman and fluorescence spectrometer that can characterize minerals and organic molecules. The team leader in charge of the instrument, Luther Beegle of NASA’s Jet Propulsion Laboratory, says that when martian samples are one day analyzed on Earth, “it will be nice to correlate what we saw, what labs see, what the geological setting is. That’s something we’ve been looking forward to.” The instruments should also be able to determine whether organics that the lander detects are native to Mars or came from a meteorite that bombarded Mars.

Much of what the Mars 2020 rover will take to Mars is similar to what’s gone before, but it’s taking one instrument that’s totally different. “We want to demonstrate we can change CO2 into O2,” Michael Hecht of the Massachusetts Institute of Technology’s Haystack Observatory says. The Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) that he’s in charge of works something like a reverse fuel cell, he explains. It uses electrolysis to split CO2 into CO and oxygen ions. A membrane then separates out the oxygen ions when heated to 800 °C, and those species combine to form diatomic oxygen molecules. “Have you seen The Martian?” Hecht asks. “MOXIE is the oxygenator” in that film.

Unlike in that movie, where the main character uses the oxygenator to create oxygen so he can breathe, MOXIE’s main goal is to demonstrate it can make oxygen to fuel future Mars explorers’ return trip. Hecht says a rocket capable of launching a crew and its equipment into orbit from Mars would need to be propelled by about 7 metric tons of methane and 27 metric tons of oxygen. Getting all that oxygen to Mars would require many launches, but if a machine like MOXIE was sent ahead of time, it could produce the required oxygen for a return trip over several years. MOXIE is supposed to make about 10 g of oxygen per hour.

Three rovers

China’s rover will be its second attempt to reach Mars, after a joint effort with Russia crashed in 2012 before leaving Earth’s orbit. HX-1 will reportedly carry a mast-mounted laser-induced breakdown spectrometer similar to the ChemCam on Curiosity and the Supercam on NASA’s Mars 2020 rover. The Chinese have done “a fair amount to imitate the ChemCam on Curiosity, same as we’re doing, so it will be fun to compare,” says Roger Wiens of Los Alamos National Laboratory, the SuperCam team leader. Like NASA’s Mars 2020 rover, HX-1 will also have a ground-penetrating radar, which can reveal geological features several meters deep. The orbiter that will accompany HX-1 to Mars carries a methane-sensing instrument as well. Methane can be a product of biological activity and has been detected on Mars before, although its source remains a mystery.

The CNSA has said it is planning to launch the rover next year, but media outlets have reported some problems with the heavy-lift rocket it intends to use for launch. The agency said it could move the mission to 2022 if it isn’t ready next year.

If China is successful, it will be just the fourth nation to reach Mars. And if the US, Europe, and China are successful, it will be the first time three rovers will operate on the Red Planet simultaneously, let alone three rovers from different nations.

Their success will also give scientists brand-new information about the planet. The novel experiments on Rosalind Franklin and NASA’s Mars 2020 rover could answer questions about Mars in new ways. And even if those ambitious plans don’t materialize, all three rovers will be collecting data about sites that scientists have never explored before, giving rise to excitement. “The fact there are three rovers headed to Mars is amazing,” Wiens says. “The success of any of those three is not assured. It’s still very much a risky business. But I can imagine the scientific conferences that would come from having three rovers in three different parts of the world.”

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Comments
Mat (July 22, 2019 1:48 PM)
A good spot to send hx1 would be under the clouds of arsia mons. Send instruments on board to see how much the clouds block radiation from space. Scout out area to send humans there. Balloons sent up from a high elevation on land below the clouds could potentually collect water from the clouds with a solar powered condenser. Water collected from clouds would need less filtering than collecting it from frozen mud.

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