A small basin (center foreground) lies below the southern rim of Melas Chasma, part of Valles Marineris on the surface of Mars. This is one of eight potential landing sites where NASA may send its Mars 2020 rover.

While it's always difficult to choose just one best landing site on Mars, NASA officials say they have made progress on picking a location for the Mars 2020 rover.

In August 2015, NASA reduced the next Red Planet rover's landing zone from an initial list of 54 locations to eight high-priority sites, said Michael Meyer, lead scientist for NASA's Mars Exploration Program, in a statement from the agency. Another workshop will take place in February, and as with other Mars landing site workshops.

NASA is also holding workshops for a possible future human landing site mission, which would take place in the 2030s, if the agency's current schedule holds. [NASA's 2020 Mars Rover in Pictures]

Making the choice

Many missions have landed on Mars, and each one has required a precise landing zone that is selected beforehand; typically, those landing zones are chosen because they support each mission's specific objectives. In the case of Mars 2020, scientists are looking for a spot that could have supported life in the ancient past, according to the statement. Specifically, they are looking for a spot that hosted water, such as along an ancient shoreline.

Once the potential mission landing sites for Mars 2020 are narrowed further, NASA will use high-resolution imagery from the Mars Reconnaissance Orbiter to do some scouting of the potential landing sites. This is being done today for potential human missions to Mars, even though that will be decades away.

In the statement, Meyer also paid tribute to the "spectacular" involvement of the broader science community, which helps decide which sites are best for Mars landings. Last week, he gave an update on the site selection process at the American Geophysical Union's annual meeting in San Francisco, along with Alex Longo (a high school student who has proposed landing sites) and Bethany Ehlmann (a scientist from NASA's Jet Propulsion Laboratory who works on both the Mars Reconnaissance Orbiter and the Curiosity rover).

A workshop in 2015 focused on landing sites for a human Mars mission brought up 47 potential landing sites where NASA would set up a semipermanent base. Crews would then perform exploration in a 60-mile (100-kilometer) radius from that zone. The location will be narrowed with future workshops and reconnaissance, according to the statement.

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