Everything about getting to Mars is difficult, but if we’re going to go through the infamous “six minutes of terror,” that NASA scientists describe as the descent to the red planet, the least we can do is make the landing site as valuable for science — and terror-free! — as possible.

A flock of scientists and Mars enthusiasts are in Glendale, California this week for a three-day gathering dedicated to one purpose: debating with each other over the best landing & research area for the Mars 2020 rover.

The meeting is the fourth in four years that has resulted in the list of possible sites being whittled from 30 down to eight, and then to a final four. At the end of the third workshop in 2017, there were actually only three finalist sites — Columbia Hills, Jezero Crater, and Northeast Syrtis — but a fourth contender was brought forth by scientists this past July. It’s between Jezero Crater and Northeast Syrtis and named Midway.

On Thursday afternoon, after much debate among the 226 attendees, there will be only one site left, and it will be recommended to NASA headquarters in Washington, D.C. as the best location for the Mars 2020 rover to hit the ground. From there, it’s up to Thomas Zurbuchen, NASA’s Associate Administrator of the Science Mission Directorate, to decide where the rover will call home.

Ken Farley, project scientist at NASA’s Jet Propulsion Laboratory, the facility managing development of the Mars 2020 Rover, said ahead of the conference that he was looking forward to the arguments to come.

“I have attended all the workshops so far, and none have disappointed when it comes to intelligent advocation and lively debate,” Farley said in a statement. “But this is what science is all about — the cogent and respectable exchange of ideas. The passion of the participants shows just how much they care about Mars exploration. They know they are playing a key role in the process, and they know how important the landing site for Mars 2020 will be.”

The Mars 2020 rover.

Why Choosing the Right Mars Landing Site is Important

The gravity of choosing a site lies in both keeping the spacecraft safe and tailoring the type of research to be performed. For example, scientists rule out places with high elevation, steep slopes, or thick dust, as they have high potential to damage the rover or lander. They also favor the equator, as the seasons are milder and the sun provides more consistent sunlight for solar panels. At this point, each site qualifies as acceptable in risk, leaving the science to guide the final decision.

“Whichever landing site is ultimately chosen, it may hold the very first batch of Mars soil that humans touch,” says Zurbuchen, noting that this choice will shape the next decade of Mars exploration.

Mars 2020 rover landing sites. This animation shows three potential sites, but a fourth contender was added in July. Scientists will determine the final one Thursday in LA.

Where Will the Mars 2020 Rover Land on Mars?

As of the last workshop, Jezero Crater and Northeast Syrtis originally held the position as the favorites. Jezero Crater, the site of what once was a lake, holds promise of learning about Mars’ carbon cycle, but isn’t optimal for taking samples to one day return to Earth. Northeast Syrtis, which housed volcanic activity, has rocks that appeal to scientists to learn about Mars’ early history and climate.

The Jezero Crater delta once housed a lake. Since the area once housed water, the remaining clay makes it a promising site to seek signs of ancient life. NASA

Scientists deemed Columbia Hills a less optimal site, but kept it as a choice as a useful target to learn about ancient Martian life and its rating with high potential for returnable samples. Since Spirit has already been here, scientists figure that other sites may result in newer, more promising findings.

Mineral springs once existed in Columbia Hills -- a fact we know thanks to NASA's Spirit rover. NASA

Finally, Midway cropped up as an opportunity to get the best of both worlds, between Jezero Crater and Northeast Syrtis.

What Will the Mars 2020 Mission Do?

The Mars 2020 mission aims to learn about the history of Mars’ environment, look for evidence of past life (which will inform whether future life could reside there), take samples that may one day be returned to Earth, and take measurements in preparation for a crewed mission. NASA plans to launch on July 17, 2020.

The six-wheeled, recently painted Mars 2020 rover is currently nameless. But, in keeping with tradition established for NASA’s Mars rovers since 1997, NASA will hold a contest challenging kids K-12 to name the rover during the 2019 school year.

What’s Next

After lunch on Thursday, attendees will pack into the Hilton’s ballroom, take two final hours to consider the arguments presented by their colleagues, and take a vote. Whether we explore a fossilized delta or the remains of hot springs, the next rover holds the future of humanity in its robotic arm.