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

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

ADVERTISEMENT

In brief

Three rovers will launch to Mars in 2020 aiming for different landing sites. The US mission, theChinese mission, and a joint European-Russian mission will all pack chemical and geological instrumentson their rovers to answer questions about Mars’s past habitability and whether life ever existed there. TheEuropean rover will drill for samples 2 m below Mars’s surface for the first time. NASA’s rover will collectand store samples to be returned to Earth at a later date for advanced analysis. It will also test aninstrument that could aid future exploration by humans on the Red Planet. China’s would be the country’sfirst 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 RedPlanet, that’s the time to do it. And that’s exactly what the US, Europe, Russia, and China plan to do nextyear.Three missions are scheduled to blast off in July 2020: NASA’s Mars 2020; ExoMars 2020, run jointly bythe European Space Agency (ESA) and Russia’s Roscosmos; and the Mars 2020 mission of the ChinaNational Space Administration (CNSA). The first mission aims to, for the first time, collect martian samplesthat will one day be returned to Earth. The second plans to drill deeper than ever before beneath Mars’ssurface, 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 forevidence that life existed—or exists—on the Red Planet. NASA’s mission will also test equipment thatcould be used in a future mission in which humans travel to Mars. If all three rovers land successfully andare 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 RiceUniversity.

Sticking the landing

The trip to Mars takes about 7–10 months. After escaping Earth’s gravity, each spacecraft will keep movingoutward 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’satmosphere. Although the atmosphere is thin, it still contains air molecules that cause friction. A heat shieldprotects the spacecraft as it plunges through these molecules toward the surface. And a specially designedparachute or parachutes deploy to slow the spacecraft to hundreds of kilometers per hour as it continues toplummet toward Mars. Rockets then fire to slow the craft further.

Sign up for C&EN's must-read weekly newsletter

Subscribe »

Contact us to opt out anytime

All of this takes about 7 minutes. But because 14 minutes are required for a signal to travel between Earthand Mars, NASA calls these 7 minutes the “7 minutes of terror,” during which scientists don’t know if thespacecraft has made it safely. The time delay also means a craft has to find its way to the surface withouthuman control.

After the rockets fire, the three missions will diverge in terms of how they’ll get their craft to the ground. TheCNSA will inflate airbags to cushion its craft’s impact, according to news reports. These will deflate afterthe 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 itsKazachok landing platform’s rockets until it is within a few meters of the surface. The Rosalind Franklinrover should then land softly on shock-absorbing legs. The previous ESA-Roscosmos mission to Mars, in2016, used a similar Russian lander called Schiaparelli, which crashed into the planet at more than 500km/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 landthe Curiosity rover, which is still operating on Mars. About 20 m from the surface, the lander will lower therover softly onto the ground on cables, then detach and fly away to crash-land at a safe distance. TheNASA spacecraft will use new technology to pick a safe landing site. Onboard cameras and computers willcompare the surface with stored photographic maps of Mars, and the craft should be able to change itslanding 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 someunique ones.

Mars 2020

mailto:cen-newsletters@acs.org

Credit: NASA/JPL-CaltechOperator: US Key feature: Caching samples for a possible future return to Earth Landing site: Jezero crater, site of an ancient delta Selected instruments: Camera, ground-penetrating radar, laser-induced breakdown spectrometer, oxygenexperiment, Raman spectrometer Planned duration: 669 Mars days Rosalind Franklin

Credit: ESA/ATG MedialabOperator: Europe

Key feature: Drilling to find evidence of life protected from Mars’s harsh surface conditions Landing site: Oxia Planum, where waterways may have flowed into a vast sea Selected instruments: Camera, gas chromatograph/mass spectrometer, infrared spectrometer, laserdesorption mass spectrometer, Raman spectrometer Planned duration: 218 Mars days HX-1

Credit: Xinhua via Getty ImagesOperator: China Key feature: Would be China’s first successful Mars mission Landing site: Unknown Selected instruments: Camera, laser-induced breakdown spectrometer, ground-penetrating radar Planned duration: 90 Mars days

On the surface

One of Earth’s defining features is its geological activity. Plate tectonics, volcanoes, and liquid water haveshaped and reshaped our planet over its history. Mars is much less active, but scientists are confident ithad some or all of those features in its past. Those types of ancient geological activity, combined withmeteorite impacts, have produced a diversity of features on the Red Planet, including mountains, lakebeds, 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,” saysRaymond E. Arvidson, a geologist at the University of Washington in St. Louis. The next best thing, hesays, 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 AgencySpirit found evidence of a hot spring or volcanic vent in a crater on Mars. Opportunity found minerals thatform where water flows on an open plain. Curiosity landed in another crater, called Gale crater, which isthought to have once held a shallow lake that evaporated over time, leaving sedimentary rocks and otherminerals behind.

NASA’s Mars 2020 rover—which will be named in a contest later this year—is going to land in Jezerocrater, whose main attraction is an ancient delta where a river once flowed into a large lake or sea. TimothyA. Goudge, a geologist at the University of Texas at Austin, says the new landing technology on the Mars2020 craft is what enables us to explore this site, which was discovered only in 2005. “Jezero was actuallyin the running for the landing site for Curiosity” in 2012, he says, but it didn’t make the cut because thechance of safe landing was too low back then.

ADVERTISEMENTSCROLL TO CONTINUE WITH CONTENTADVERTISEMENTSCROLL TO CONTINUE WITH CONTENTGoudge, who advocated for Jezero during NASA’s 2020 landing-site selection process, says the site has anumber of geological features to explore. The delta would have collected water and sediment from awatershed of 30,000 km , he says. That makes it a good place to look for signs of life. “Deltas are goodcollectors 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 ofthe oldest martian crust.

Goudge notes that Mars orbiters—spacecraft that circle the Red Planet rather than land on it—havedetected outcroppings of carbonate minerals in Jezero from afar. Scientists think it’s likely that atmosphericcarbon dioxide created a greenhouse effect that transformed Mars from a wet planet to the dry one we seetoday. That CO should be stored in these carbonate minerals, but rovers haven’t found the physicalevidence to back up the theory. NASA’s Mars 2020 mission may change that and answer questions aboutthe 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 orfrom the collection of Mars meteorites,” says Kenneth A. Farley, a geochemist at the California Institute ofTechnology who’s the project scientist for NASA’s Mars 2020 mission.

2

2

China hasn’t announced where its rover will land, but the European and Russian ExoMars mission isshooting for a plain called Oxia Planum. Similar to Jezero crater, Oxia Planum is thought to hold claydeposits left over from an ancient body of water that flowed out of several waterways. The site is at theoutflow of one of the largest systems of ancient waterways on Mars, according to Jorge Vago, the projectscientist at ESA for the ExoMars 2020 mission. One thing that makes Oxia Planum especially interesting toVago is that the body of water may have been very large, even an ocean. The past existence of a northernmartian 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 missionis not about geology, not about minerals. The mission is about chemistry.” Specifically, chemical evidenceof 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/CornellUniversity (Spirit & Opportunity artist rendering); NASA/JPL-Caltech/MSSS (Curiosity); NASA/JPL-Caltech(Insight artist rendering, Mars 2020 artist rendering); ESA/ATG Medialab (Rosalind Franklin artistrendering); Xinhua via Getty Images (HX-1 artist rendering); USGS Astrogeology Science Center (landingsites)

https://cen.acs.org/physical-chemistry/astrochemistry/ESA-names-Mars-rover-chemist/97/web/2019/02

Credit: USGS Astrogeology Science CenterThe landers and rovers that have successfully touched down on Mars have done so in regions scatteredacross 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 haveexisted 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 biosignaturesthat 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 fieldshield 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 thatthey’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 tounearth samples that have been shielded from both radiation and oxidizing chemicals like perchlorates inMars’s atmosphere, says François Raulin, an emeritus professor at University Paris-Est Créteil Val deMarne and coleader of the team that designed the Mars Organic Molecule Analyzer (MOMA), which willanalyze drilled samples.

Whether the drill can work as planned remains to be seen. NASA’s InSight lander, which touched down onMars in 2018 and is still in operation, also has a drill meant to dig as deep as 5 m. But it has a differentdesign. It got about 30 cm down before it stopped moving, possibly because it ran into a rock. Scientistsand 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 tovolatilize molecules in samples that are brought up by the drill, then analyze those with gaschromatography/mass spectrometry and laser desorption mass spectrometry. The GC/MS and LD-MSinstruments share a single linear ion trap to carry out the analysis. It was selected for its small size andability to operate at ambient Mars pressure rather than under high vacuum. MOMA also carries reagentsthat can be added to samples to volatilize chiral molecules, small molecules like amino acids, and verylarge molecules intact.

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

Advertisement

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

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

After analysis by Ma_MISS but before MOMA, samples are analyzed by an infrared spectrometer, whichwill be used to determine minerals’ composition and origin, and a Raman spectrometer. Raulin saysRaman spectra are a good place to look for organic molecules. “If we clearly see organics from IR andRaman, 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 somethingsuggestive of life, though, is about 50-50. “Remember, we’re talking about something that may have beenalive 4 billion years ago,” he says. On Earth, something that age would be too degraded to detect, Vagoadds, but Mars’s cold, preserving temperatures and more recent geological quiescence mean scientistsmight get lucky.

The fact there are three rovers headed to Mars is amazing.Roger Wiens, SuperCam team leader, Los Alamos National Laboratory

Credit: NASA/JPL-CaltechEngineers 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 inSt. 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 saysenthusiasm for Mars exploration in the US fell off quickly when it became clear there was no evidence ofbiological activity in the soil. The orbiting Mars Global Surveyor in the 1990s sparked new interest instudying martian geology, and the next rovers, Spirit and Opportunity, were essentially doing robotic fieldgeology. Curiosity’s mission looked at the role water played on Mars and has evolved to explore theplanet’s past habitability. All these missions carried the analytical equipment on board to answer thosequestions 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 foranalysis, Arvidson says.

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

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

In addition to performing some experiments similar to other Mars missions, NASA’s Mars 2020 rover willcollect at least 20 pencil-sized cores drilled from martian rocks, seal them in tubes, and store them. Whatcomes next is still only a guess, but scientists are confident that NASA will fund a mission to retrieve thosesamples. 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 toretrieve the cached samples and a rocket to propel them into Mars orbit. There, the samples would betransferred to an orbiter that could return them to Earth. NASA scientists had talked about launching thosemissions in the late 2020s, but Michael Meyer, NASA’s lead scientist for Mars exploration, said at a Marsexploration 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 nevercollect those, the mission is by no means a bust,” Arvidson says. The data collected by the experimentscarried 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 suitableplaces to collect samples and provide context about them. The Scanning Habitable Environments withRaman and Luminescence for Organics and Chemicals instrument, or SHERLOC, has a deep-ultravioletRaman and fluorescence spectrometer that can characterize minerals and organic molecules. The teamleader in charge of the instrument, Luther Beegle of NASA’s Jet Propulsion Laboratory, says that whenmartian 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 shouldalso be able to determine whether organics that the lander detects are native to Mars or came from ameteorite 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 oneinstrument that’s totally different. “We want to demonstrate we can change CO into O ,” Michael Hecht ofthe Massachusetts Institute of Technology’s Haystack Observatory says. The Mars Oxygen In-SituResource Utilization Experiment (MOXIE) that he’s in charge of works something like a reverse fuel cell, heexplains. It uses electrolysis to split CO into CO and oxygen ions. A membrane then separates out theoxygen ions when heated to 800 °C, and those species combine to form diatomic oxygen molecules. “Haveyou 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. Hechtsays a rocket capable of launching a crew and its equipment into orbit from Mars would need to bepropelled by about 7 metric tons of methane and 27 metric tons of oxygen. Getting all that oxygen to Marswould require many launches, but if a machine like MOXIE was sent ahead of time, it could produce therequired oxygen for a return trip over several years. MOXIE is supposed to make about 10 g of oxygen perhour.

2 2

2

Three rovers

China’s rover will be its second attempt to reach Mars, after a joint effort with Russia crashed in 2012before leaving Earth’s orbit. HX-1 will reportedly carry a mast-mounted laser-induced breakdownspectrometer similar to the ChemCam on Curiosity and the Supercam on NASA’s Mars 2020 rover. TheChinese have done “a fair amount to imitate the ChemCam on Curiosity, same as we’re doing, so it will befun to compare,” says Roger Wiens of Los Alamos National Laboratory, the SuperCam team leader. LikeNASA’s Mars 2020 rover, HX-1 will also have a ground-penetrating radar, which can reveal geologicalfeatures several meters deep. The orbiter that will accompany HX-1 to Mars carries a methane-sensinginstrument 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 someproblems with the heavy-lift rocket it intends to use for launch. The agency said it could move the missionto 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 aresuccessful, it will be the first time three rovers will operate on the Red Planet simultaneously, let alonethree rovers from different nations.

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

Chemical & Engineering NewsISSN 0009-2347Copyright © 2019 American Chemical Society