Three possible landing sites are now in the running for NASA's Mars 2020 rover.

NE Syrtis Major
A huge inactive shield volcano in NE Syrtis Major.
NASA / JPL-Caltech / University of Arizona

And then there were three. Researchers participating in a workshop held early this month in Monrovia, California, narrowed down the potential landing sites for the Mars 2020 rover to three locations: Columbia Hills, Jezero Crater, and Northeast Syrtis.

The sites selected include regions where water may have flowed and, just possibly, microbial Martian life might once have flourished. The selection process whittled down the three remaining contenders from eight earlier selections.

"The primary scientific factors that drive site selection for the Mars 2020 rover are evidence for an ancient environment with high habitability potential, biosignature preservation potential, and geologic diversity," says Ken Williford (NASA-JPL). "Scientists are particularly interested in landing sites where spectroscopic data from orbit indicate the presence of water-containing minerals in association with these ancient habitable environments."

NASA landing sites
NASA's past landing sites on Mars (yellow) versus the three proposed landing sites (red) for the Mars 2020 rover.
NASA / JPL, with modifications by Dave Dickinson

Here's a brief rundown of the finalists:

Columbia Hills: Mineral springs once came to the surface here in warmer times. If the Columbia Hills region sounds familiar, that's because NASA's Spirit rover explored the region until it finally fell silent in 2010. Spirit's discovery of ancient hot springs in Columbia Hills came as a surprise, and researchers now suspect that a shallow lake once filled the 100-mile (160-kilometer) wide Gusev Crater. If Columbia Hills site is selected, we just might see another first, when the Mars 2020 rover rolls up to the now derelict Spirit rover.

Columbia Hills
Columbia Hills as seen from NASA's Spirit rover.
NASA / JPL-Caltech / Cornell

Jezero Crater: A more daring and remote choice compared to previous NASA landings, Jezero Crater may have flooded and drained at least twice via now-dried-up river channels, which once carried water and clay minerals. Microbial life might have made a home in the crater 3.5 billion years ago.

A false color view of Jezero Crater, showing sediments that have undergone alteration due to chemical interaction with water. NASA/JPL-Caltech/MSSS/JHU-APL
A false color view of Jezero Crater, showing sediments that have undergone alteration due to chemical interaction with water.

Northeast Syrtis: Located near Jezero Crater, volcanic activity may have provided a warm niche for life to flourish here in the early days of Mars. Today, the layered terrain holds a rich record of diverse activity and interactions between minerals and water. It's a place where the chemical reactions leading to life could conceivably have taken hold.

Mars Reconnaissance Orbiter on the Hunt

Analysis of the candidate sites comes courtesy of NASA's Mars Reconnaissance Orbiter (MRO), in orbit around the Red Planet since 2006. With its 0.5-meter aperture HiRISE camera, MRO gives NASA the equivalent of spy satellite resolution from low orbit. The spacecraft has been circling Mars long enough to see changes in sites over the past decade.

“Whether it is looking at the surface, the subsurface, or the atmosphere of the planet, MRO has viewed Mars from orbit with unprecedented spatial resolution, and that produces huge volumes of data,” says MRO project scientist Rich Zurek (JPL-MRO) in a recent press release. “These data are a treasure trove for the whole Mars scientific community to study as we seek to answer a broad range of questions about the evolving habitability, geology, and climate of Mars.”

MRO will have passed along an amazing 300 terabits of information this year, more than every other interplanetary mission combined. MRO has mapped 99% of the surface of Mars down to a resolution of 25 meters or better, including high-resolution swaths over selected sites down to better than a meter resolution. Data collected from MRO will also be incorporated during eventual site selection for crewed missions to Mars in the 2030s.

Mars 2020 versus Curiosity

The Mars 2020 rover resembles Curiosity on the exterior, and like its older sibling, the Mars 2020 rover will land via sky crane and sport a plutonium-fueled nuclear Radioisotope Thermoelectric Generator (RTG). However, the Mars 2020 rover will use a range trigger during the Entry, Descent and Landing (EDL) phase, which will allow the lander to decide when to open the parachute, reducing the size of the landing ellipse.

Also unlike Curiosity, the Mars 2020 science packages will directly target the question of whether life ever existed on Mars. Moreover, Mars 2020 rover will carry 40 empty tubes for rock cores, with the aim of collecting a cache of surface material for a possible automated sample return mission in the future.

"We can choose a final landing site as late as one year prior to launch," says Williford. "But our goal is to have site selection finalized by two years prior to launch."

Mars 2020 will launch on an Atlas 5 rocket in July 2020 from Cape Canaveral. It should arrive at Mars in early 2021.

If all goes as planned, humanity will really start to invade Mars in the next two launch windows. Only one mission, the European Space Agency (ESA) ExoMars Trace Gas Orbiter and ill-fated Schiaparelli Lander made the trip to Mars in 2016. With Mars launch windows coming around about every 26 months, the next one will arrive in 2018. Watch for NASA's Mars InSight and possibly SpaceX's Red Dragon lander to make the trip then. All four potential landing sites for Mars InSight are within a landing ellipse in Elysium Planitia.

The 2020 mission roll call is far larger, and should include the Mars 2020 rover (it'll have a proper name like every other NASA rover by then), the United Arab Emirates' Mars Hope orbiter, a possible rover fielded by China, ESA's ExoMars rover, and India's second Mars mission.

Get ready as Mars exploration kicks into high gear.


Mars 2020


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February 18, 2017 at 1:11 pm

The Curiosity rover entry phase did use a range trigger for parachute deployment to reduce the size of the landing ellipse, subject to Mach number and dynamic pressure constraints.

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David Dickinson

February 19, 2017 at 10:02 am

Dunno what to say... here's a quote as per Ken Williford, JPL-Deputy Project scientist: "The entry, descent and landing (EDL) system for Mars 2020 is very similar to that for the Curiosity rover, with some minor, but important improvements. The first is called “range trigger” and allows greater control on when the parachute opens thereby reducing the size of the landing ellipse. The second is called “terrain relative navigation” and allows the spacecraft to detect and avoid previously identified hazardous areas in the landing ellipse on its way to the surface. This capability enables the rover to land closer to the rock outcrops of greatest scientific interest."
Hope this helps,
Dave Dickinson

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February 21, 2017 at 6:41 pm

Yes, you are correct. Sorry about that. The range trigger logic was used in our performance analysis version when I was working with that project, but I retired from NASA before the Curiosity mission actually flew. I've found out that the range trigger option was pulled prior to the Curiosity flight out of concern that unknown navigation problems might possibly cause a false trigger of the deployment. However, the confidence level in the entry phase guidance and navigation performance is much higher now, and the range trigger logic has been approved for use in 2020. That's good news, because it does result in a significant improvement in the precision landing performance, especially in dispersed environmental conditions.
Gil Carman

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February 20, 2017 at 2:03 pm

Wow—great article on all the busy international preparations for upcoming explorations of Mars. I hope this spurs greater US spending on space exploration, instead of Congress’s usual pinchpenny approach, if only because highly competitive America usually wants to be the best, fastest and firstest (!) in any field of endeavor.

By the way, just below the subheading “Mars 2020 versus Curiosity” you say “The Mars 2020 rover resembles Curiosity on the exterior, and like its younger sibling, the Mars 2020 rover will land via sky crane and sport a plutonium-fueled nuclear Radioisotope Thermoelectric Generator (RTG).” Isn’t Curiosity Mars 2020’s OLDER sibling? My sister was born first and that makes her older than me. Same should be true of Curiosity vis-à-vis Mars 2020.

Maybe I’m just reading it wrong...

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