The European Space Agency has announced four candidate landing sites for the ExoMars rover, as a deadline looms to secure full funding for the mission in time for a scheduled launch to the red planet in 2018.
Considered the cream of a crop of eight proposed landing sites, the four locations selected by a group of European, Russian and U.S. scientists are clustered near the Martian equator.
The four landing site finalists — Mawrth Vallis, Oxia Planum, Hypanis Vallis and Aram Dorsum — will be whittled down to a single preferred destination for ESA’s ExoMars rover by October 2017.
The solar-powered rover and its landing platform are scheduled to launch aboard a Russian Proton booster during an 18-day window opening May 7, 2018. Guided through the Martian atmosphere by a Russian descent system, the rover will land on the red planet in January 2019 to begin a seven-month prime mission covering up to 4 kilometers of driving.
ESA entered a partnership with Roscosmos, the Russian Federal Space Agency, after NASA backed out of a major role in the ExoMars project in 2012 due to budget limitations. The U.S. space agency was supposed to provide two Atlas 5 launchers, along with science instruments and a sky crane landing system, for a European-built ExoMars orbiter for liftoff in 2016 and the ExoMars rover in 2018.
NASA is still paying for components for one of the rover’s major instruments, an astrobiology sensor designed to search for the building blocks of life in Martian soil.
The ExoMars rover will weigh about 660 pounds, or 300 kilograms, when it launches cocooned inside a Russian-built descent and landing system.
Outfitted with a drill to extract soil up to 2 meters, or 6 feet, below the Martian surface, the the mobile robot is the first European Mars rover. Its international complement of instruments will analyze Martian soil, including underground samples for the first time, for signs of organic material and biomarkers indicative of ancient life.
Russia took over responsibility for the elements of the ExoMars mission abandoned by NASA.
ESA Director General Jean-Jacques Dordain told reporters at the 65th International Astronautical Congress last week that the ExoMars mission has encountered “no interference whatsoever, for the time being,” caused by worsened diplomatic relations between Russia and Western nations.
“We have no interference from the political situation in our cooperation with Russia,” Dordain said. “I have not received any guidelines from the member states to restrict the ongoing cooperation, and I have not received any signal from Russia that they are trying to restrict their ongoing cooperation with ESA.”
Activity is on track for liftoff of Europe’s Mars Trace Gas Orbiter, the first of a two-launch set of ExoMars missions, in January 2016, officials said.
Like the 2018 rover, the European Mars orbiter and a piggyback entry, descent and landing demonstrator will launch on a Russian Proton rocket from the Baikonur Cosmodrome in Kazakhstan.
The Mars Trace Gas Orbiter is in final assembly at a Thales Alenia Space facility in France. Final testing of the orbiter and the lander, dubbed Schiaparelli, will begin next year before shipment to the Baikonur Cosmodrome in late 2015, Dordain said.
The budget for the 2016 ExoMars launch is in good shape, officials said, but there is a funding shortfall to complete payments for the 2018 mission.
“For the 2018 mission, we are, technically speaking, on schedule,” Dordain said. “But I am missing money for the 2018 mission.”
Dordain said he will seek final ExoMars funding commitments from ESA member states when government representatives meet Dec. 2 in Luxembourg to iron out plans for a future European launcher and extended ESA participation in the International Space Station.
“I hope I should be able to complete the funding for the 2018 mission by December of this year,” Dordain said.
Work to prepare for the European rover mission has continued unabated despite the funding woes. The British division of Airbus Defence and Space, the lead contractor for development of the rover itself, has begun ordering parts for the spacecraft.
The latest sign of progress came with ESA’s announcement Oct. 1 of the rover’s four candidate landing sites.
The prospective landing zones all show evidence of the ancient presence of water.
“The present-day surface of Mars is a hostile place for living organisms, but primitive life may have gained a foothold when the climate was warmer and wetter, between 3.5 billion and 4 billion years ago,” said Jorge Vago, ESA’s ExoMars project scientist.
“Therefore, our landing site should be in an area with ancient rocks where liquid water was once abundant,” Vago said. “Our initial assessment clearly identified four landing sites that are best suited to the mission’s scientific goals.”
Two of the sites, Mawrth Vallis and nearby Oxia Planum, contain rocks older than 3.8 billion years old and rich in clay minerals, an indicator that water was once present there. The clays were exposed by erosion relatively recently in Mars geologic history, reducing chances the material was altered by radiation and oxidation, according to an ESA press release.
The Hypanis Vallis site is situated on an ancient river delta at the end of a network of channels that may have once led into a Martian lake.
Located along a channel surrounded by sedimentary rocks, the Aram Dorsum location may have been home to a river billions of years ago.
“This region experienced both sustained water activity followed by burial, providing protection from radiation and oxidation for most of Mars’ geological history, also making this a site with strong potential for finding preserved biosignatures,” ESA said in a press release.
“While all four sites are clearly interesting scientifically, they must also allow for the operational and engineering requirements for safe landing and roving on the surface,” Vago said. “Technical constraints are satisfied to different degrees in each of these locations and, although our preliminary evaluation indicates that Oxia Planum has fewer problems compared to the other sites, verification is still ongoing.”
For safety reasons, engineers say the rover’s landing site should be free of steep slopes, large rock fields, be near the equator and at a low elevation.
While the ExoMars technical team keeps preparing for the launch of Europe’s first Mars rover, Dordain is charged with wading through political waters to secure funding commitments to make the mission happen.
Italy is the largest financial contributor to ESA’s $1.5 billion (1.2 billion euro) ExoMars program. Britain is the second-largest backer.
Germany and France, ESA’s largest member states, have lesser roles in the ExoMars program.
The question of where to look for more ExoMars money has followed ESA’s leaders for years, but with major construction of the rover starting to kick off, time is running out to make up the budget shortfall in order to make the May 2018 launch opportunity, which is governed by the alignment of the planets.
The next launch opportunity to Mars comes in the summer of 2020.