Gearing up for its ambitious Mars mission in 2016, NASA has narrowed down to four potential landing sites with an aim at studying the red planet’s interior.

The mission will touch down at one of the four sites selected in August from a field of 22 candidates.

Briefing about the selected sites, NASA said, “All four semi-finalist spots lie near each other on an equatorial plain in an area of Mars called Elysium Planitia.

“We picked four sites that look safest. They have mostly smooth terrain, few rocks and very little slope,” said geologist Matt Golombek of NASA’s Jet Propulsion Laboratory in Pasadena, California.

Unlike previous Mars landings, what is on the surface in the area matters little in the choice of a site except for safety considerations.

Each semifinalist site is an ellipse measuring 130 kilometres from east to west and 27 kilometres from north to south.

Engineers calculate the spacecraft will have a 99-percent chance of landing within that ellipse, if targeted for the center.

The stationary Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport (InSight) lander is scheduled to launch in March 2016 and land on Mars six months later.

Elaborating upon the next move, NASA said, “We will focus two Mars Reconnaissance Orbiter cameras on the semi-finalists in the coming months to gain data. These data will be used to select the best of the four sites well before InSight is launched.

What is 2016 Mars Mission?

NASA’s Mars mission aims at investigating the processes that formed and shaped Mars and will help scientists better understand the evolution of our inner solar system’s rocky planets, including Earth.

“This mission’s science goals are not related to any specific location on Mars because we’re studying the planet as a whole, down to its core,” said Bruce Banerdt, InSight principal investigator at JPL.

“Mission safety and survival are what drive our criteria for a landing site,” said Banerdt.