ExoMars: Europe's astrobiology missions to Mars

Graphic showing the exomars gas trace orbiter orbiting above the surface of Mars, the Red Planet can be seen in the distance.
Artist's illustration of the ExoMars Trace Gas Orbiter at Mars. (Image credit: ESA/ATG medialab)

ExoMars is the European Space Agency's (ESA) Mars exploration program, which consists of two missions unified in their goal to characterize the Red Planet's past habitability.

The first mission was the Trace Gas Orbiter, which launched to Mars in 2016. The second mission is the long-delayed Rosalind Franklin rover (also known as the ExoMars rover), which will launch to Mars in October 2028 on a mission to drill deeper into the Martian surface than ever before to look for evidence of past life on the Red Planet.

Rosalind Franklin will be Europe's first Mars rover. It is equipped with a drill that can dig about 6.5 feet (2 meters) into the ground, according to ESA. In doing so, the Rosalind Franklin rover will be able to search for biomarkers — chemical evidence of life, such as complex organic molecules — that have been buried and protected from radiation for 3 billion to 4 billion years, all the way back to when Mars was warmer and wetter.

Related: Mars missions: A brief history 

When will the Rosalind Franklin rover launch?

The Rosalind Franklin rover is currently scheduled to blast off in 2028, according to ESA, with the aim of landing on the Red Planet in 2030. 

The rover has been delayed several times. Originally scheduled for launch in 2018, the early stages of the mission's development were plagued by technical difficulties. One significant setback was the failure of the Schiaparelli Entry, Descent and Landing Demonstrator Module (EDM). Designed as a prototype to test how Rosalind Franklin would land on the surface, it traveled to the Red Planet in 2016 by piggybacking on the Trace Gas Orbiter. Once in Mars orbit, Schiaparelli was deployed, but the lander crashed into the ground.

The COVID-19 pandemic led to another launch delay, with the second half of 2022 then being targeted. The ExoMars program was a joint initiative between ESA and the Russian space agency, Roscosmos. The rover was meant to launch on a Russian Proton rocket and be taken down to the Martian surface by a Russian landing platform called Kazachok, which also would have conducted imaging and climate science. 

However, following Russia's invasion of Ukraine, subsequent international sanctions led ESA to dissolve the agreement to work with Roscosmos in July 2022, mere months before launch. The resulting unavailability of the Russian launch rocket and landing platform has led to a new and lengthy delay.

Who was Rosalind Franklin?

The ExoMars rover is named after British chemist and X-ray crystallographer Rosalind Franklin, who made many revolutionary discoveries — including the molecular structure of DNA, RNA and viruses — and may have won a Nobel Prize for her work had she not died in 1958, not long after making her revolutionary discoveries. It is a fitting name for a rover that is searching for the chemistry of possible life on Mars

Related: 20 trailblazing women in astronomy and astrophysics

How will the Rosalind Franklin rover land on Mars?

ESA's Rosalind Franklin rover is currently scheduled land on Mars in 2030. (Image credit: Adrian Mann/Stocktrek Images via Getty Images)

The Rosalind Franklin rover will touch down slightly differently than NASA's Curiosity and Perseverance rovers, which were winched to the ground by the sky crane method.

Rosalind Franklin will arrive at Mars in its carrier module — an enclosed shell around a descent module containing a heat shield, the landing platform and the rover, the latter two of which are connected. Upon nearing Mars, the descent module will detach and plummet through the atmosphere, protected by its heat shield, ESA's mission page explains. Its predecessor, Schiaparelli, reached temperatures as high as 2,732 degrees Fahrenheit (1,500 degrees Celsius) before being lost.

Hopefully, that same fate won't befall the Rosalind Franklin rover. Parachutes will deploy to slow the falling descent module. The heat shield and parachutes will detach at an altitude of about 4.3 miles (7 kilometers) above the surface, at which point retro thrusters will take over for most of the remaining journey until the rover is mere meters above the ground. At that point, the engines will switch off, and the landing platform will drop the rest of the way to a cushioned landing on airbags. Those airbags will deflate, and after various systems checks, Rosalind Franklin will be ready for egress and deployment on the Martian surface.

Where will the Rosalind Franklin rover land?

A landing site in Oxia Planum was selected in 2018. It is located near the Martian equator and features large lowland plains that were once submerged in water and fed by a multitude of rivers, which today can be seen as channels covering 82,000 square miles (212,000 square kilometers).

The plains are home to rich clay deposits that formed in the water long ago, and there are many exposed outcroppings where the Rosalind Franklin rover will be able to study stratigraphic layers, with deeper layers being the oldest. After Mars' climate changed over 3 billion years ago, a period of volcanism flooded Oxia Planum with lava, and today, many basaltic rocks still exist, protecting sediments from the rivers, lakes and seas that filled the region from the harmful radiation coming down from space.

The solar-powered Rosalind Franklin rover faces the risk that dust will accumulate on its solar panels, thus reducing the energy it receives and limiting its life span. To mitigate this risk, the Rosalind Franklin rover will touch down during springtime in Oxia Planum. The timing of this landing is outside of dust-storm season on the Red Planet, meaning that the risk to the rover, at least during the initial stages of its mission, is limited. ESA has asked NASA to add nuclear-powered radioisotope thermal generators to supply energy to heaters, to prevent the rover's circuitry and instruments from growing too cold during the chilly Martian nights. 

What will the Rosalind Franklin rover be looking for on Mars?

Given its history and geology, Oxia Planum is the perfect location to search for preserved chemical biomarkers, and even microfossils, dating back billions of years. Biomarkers are organic compounds utilized by life as we know it, including lipids such as fatty acids, as well as amino acids and nucleic acids

The Rosalind Franklin rover will drill down as deep as 6.5 feet to retrieve samples for analysis in its sophisticated onboard laboratory; there will be no sample return back to Earth as there is for NASA's Perseverance rover. The laboratory will be able to identify the minerals and organic compounds in the samples, giving a picture of the conditions in Oxia Planum long ago and answering the question of whether it was ever home to life. 

What instruments does the Rosalind Franklin rover have?

The Rosalind Franklin rover is armed with nine scientific instruments. On top of the rover's mast is PanCam, the panoramic camera, built by scientists at the Mullard Space Science Laboratory at University College London. PanCam will take most of the beauty shots of the Martian terrain, much like the Curiosity rover's Mastcam. Working in tandem with PanCam on the rover mast will be the Infrared Spectrometer for ExoMars, which will measure the mineralogy of Martian rocks. The Close-Up Imager (CLUPI) will take high-resolution close-up images of interesting geological targets. The Micromega Infrared Spectrometer (MicrOmega), a visible and infrared imaging spectrometer, will also study Martian mineralogy, identifying minerals formed in water, which could tell scientists about the history of Oxia Planum.

In the search for biomarkers, the Mars Organic Molecule Analyzer (MOMA), built by scientists at NASA's Goddard Space Flight Center, will search for chemical evidence of historic life on Mars. It will be supported by the Raman Laser Spectrometer, which will be able to identify organic pigments as well as study mineralogy.

Much of the rover's work will be done underground, especially because the rover is armed with a drill that can dig up to 6.5 feet deep and retrieve samples. Fitted inside the drill is the Mars Multispectral Imager for Subsurface Studies (Ma-MISS), which will directly assess the mineralogy and rock formations underground. Another instrument, the Russian-built Autonomous Detector of Radiation of Neutrons Onboard Rover at Mars (Adron), will search for subsurface water, in tandem with the Water-Ice and Subsurface Deposit Observation on Mars (WISDOM), ground-penetrating radar that will help identify areas where the rover can drill.

Rosalind Franklin rover: Current status

The Rosalind Franklin rover is currently being stored in an ultraclean room while engineers figure out how to detach the rover from the Russian lander that can no longer be used. As the rover sits in storage, tests continue on Rosalind Franklin's twin, a rover called Amalia that will remain on Earth as an engineering test model.

European countries will pay 360 million euros to keep the mission alive, and NASA has agreed to lend a helping hand, by providing either a new launch vehicle or a new lander, after requesting $30 million in funding from the U.S. Congress to support the mission. 

Trace Gas Orbiter and Schiaparelli

The goal of the Trace Gas Orbiter (TGO) is to search for less-abundant components of Mars' atmosphere. The Martian atmosphere is mostly made up of carbon dioxide, but concentrations of other molecules are poorly understood. For example, methane — a sign of either biological or geological activity — has been measured in different concentrations by different ground-based telescopes. The Curiosity rover has made repeated measurements of methane on the surface, but a global view of Mars would give a better sense of the methane's source or sources.

"Since methane is short-lived on geological time scales, its presence implies the existence of an active, current source of methane. It is not clear, yet, whether the nature of that source is biological or chemical," ESA stated. "Organisms on Earth release methane as they digest nutrients. However, other purely geological processes, such as the oxidation of certain minerals, also release methane."

TGO and Schiaparelli were launched together on March 14, 2016, from a Proton rocket from Baikonur, Kazakhstan. TGO successfully entered orbit at Mars on Oct. 19, 2016, the same day of Schiaparelli's landing attempt, which failed. Two days after the malfunction, NASA's Mars Reconnaissance Orbiter photographed evidence of Schiaparelli's crash site, and additional pictures were sent in over several weeks. In 2017, an ESA investigation showed that a data glitch caused the Schiaparelli crash.

Meanwhile, TGO was inserted into a highly elliptical orbit at Mars that took four Earth-days to complete. To perform its main science mission, it was lowered into a near-circular altitude of about 400 kilometers (250 miles) and had a two-hour orbit. Starting in 2017, mission controllers made a series of controlled skims through the edge of the Martian atmosphere. This technique is called "aerobraking" and has been performed by several other Mars missions, as well as the European Venus Express mission. It finished its aerobraking in February 2018 and sent its first image, of Korolev Crater, that April. More science results are expected to come now that TGO is in its main mapping orbit

TGO has four principal instruments:

  • NOMAD (Nadir and Occultation for Mars Discovery) — a package of three spectrometers (two infrared, one ultraviolet) to identify methane and other parts of the atmosphere. Some elements will be found by looking at the atmosphere with the sun behind it, while others will be examined by direct reflected-light observations.
  • ACS (Atmospheric Chemistry Street) — three infrared instruments will provide information on the Martian atmosphere's chemistry and structure.
  • CaSSIS (Colour and Stereo Surface Imaging System) — provides high-resolution images of the surface that will give geological context — and the possible sources or sinks — for trace gases found by NOMAD and ACS.
  • FREND (Fine Resolution Epithermal Neutron Detector) — maps potential deposits of water ice by looking for hydrogen on the surface to depths of up to one meter (3 feet).

Besides its science mission, TGO is expected to serve as a communications relay for the ExoMars rover when it reaches the Martian surface. (TGO was also supposed to send communications from the failed Schiaparelli lander to Earth, but that part of the mission was never realized.)

Trace Gas Orbiter discoveries

The ExoMars Trace Gas Orbiter is still actively collecting data high above the Red Planet. The orbiter will not only act as a relay for the Rosalind Franklin rover, transmitting its data back to Earth, but also actively study Mars' atmosphere.

As the mission name suggests, the aim is to chart the presence of trace gases in Mars' atmosphere — that is, gases that are in short supply but that could indicate interesting geological, atmospheric or even biological processes, in either the past or present, on Mars. For example, methane is a trace gas that has come under the spotlight in recent years thanks to anomalous plumes of the gas that have been detected by Mars Express, the Trace Gas Orbiter and the Curiosity rover. This methane on Mars could be either geological or biological in origin.

So far, the Trace Gas Orbiter has detected a possible chlorine cycle on Mars, with the discovery of hydrogen chloride in the atmosphere. The hydrogen chloride may originate in interactions between the surface and the atmosphere during dust storms, as winds lift salts such as sodium chloride into the atmosphere, where it reacts with water vapor. This releases chlorine, which then reacts with other hydrogen-bearing molecules to form hydrogen chloride.

The Trace Gas Orbiter has also been tracking water loss, as atoms of hydrogen and oxygen — the components of water — escape the atmosphere. This rate of escape tells scientists how much water Mars may have had billions of years ago, when Mars was much warmer and had a thicker atmosphere. 

Additional resources

Check out NASA's overview of the Red Planet, and The Planetary Society's guide to water on Mars Follow the latest information about robotic exploration of Mars from the ESA.

 Follow Keith Cooper on Twitter @21stCenturySETI. Follow us on Twitter @Spacedotcom and on Facebook.


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Keith Cooper
Contributing writer

Keith Cooper is a freelance science journalist and editor in the United Kingdom, and has a degree in physics and astrophysics from the University of Manchester. He's the author of "The Contact Paradox: Challenging Our Assumptions in the Search for Extraterrestrial Intelligence" (Bloomsbury Sigma, 2020) and has written articles on astronomy, space, physics and astrobiology for a multitude of magazines and websites.

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