In 2020, NASA will be sending a new rover to Mars. But where this rover will land is currently up for debate, with NASA holding workshops at the Doubletree Hotel in Monrovia, California, this week (February 8 to 10) to decide on the best location.

There are eight candidate sites currently in contention for the rover. The ideal site needs to have signs of past habitability and life, and also provide a good location for the rover to collect samples for a possible future mission to pick up and return to Earth.

At the last landing site workshop, in 2015, the highest rated landing site of the then 21 landing sites was a dry ancient lake called Jezero Crater, located in the northern hemisphere. The second highest was an interesting idea to land the rover at the same location NASA’s Spirit rover landed in 2004, Columbia Hills, which is already known to meet many of the mission requirements.

Of the eight candidate sites remaining, this workshop will whittle the list down to three or four. “Presenters at the workshop are expected to make a comprehensive, persuasive talk on why a specific site is the right one for the 2020 mission and payload, including how and where the science objectives of the mission can be accomplished,” the workshop’s website states.

A fourth workshop will then be held at some point in the future to narrow this list even further, before NASA makes its final decision.

Much of the evaluation of each landing site has been made possible by NASA’s long-serving Mars Reconnaissance Orbiter (MRO), which has been imaging the planet since it entered orbit in 2006. Using the satellite’s images, for example, scientists can create 3D views of an area and see whether it would be too steep for a rover, or if there are boulders on the ground that could be hazardous.

"From the point of view of evaluating potential landing sites, the Mars Reconnaissance Orbiter is the perfect spacecraft for getting all the information needed," said the workshop's co-chair Matt Golombek of NASA's Jet Propulsion Laboratory in Pasadena, California, in a statement. "You just can't overstate the importance of MRO for landing-site selection."

Images taken by the MRO are also being used to look at potential landing sites for humans, with about 45 locations being considered where astronauts could explore a large area 200 kilometers (120 miles) across.

The 2020 Mars Rover will be launching in July 2020 and landing in early 2021, at the same time as a European rover, ESA’s Exomars. Together, they will both perform one of the most extensive studies of past habitability on Mars, and perhaps lead us closer to discovering if life did – or still does – reside there.