InSight’s Landing Site: Elysium Planitia

Map of Mars landing sites.

InSight's Landing Site: Elysium Planitia


    InSight landed at 11:52:59 a.m. PT (2:52:59 p.m. ET) on Nov. 26, 2018 near Mars' equator on the western side of a flat, smooth plain called Elysium Planitia.

    Elysium Planitia was selected not for its surface features, but for safety considerations. InSight's purpose is to study the interior of Mars, not the surface. Thus, in the selection of a landing site, what's on the surface mattered less on this mission than for previous rover missions focused on the geology.

    Planitia is Latin for a flat surface, geometric plane or flatness or a plain. Elysium is from the ancient Greek name for an afterlife paradise, usually referred to in English as the Elysian Fields.

    The landing site lies in the western portion of Elysium Planitia, centered at about 4.5 degrees north latitude and 135.9 degrees east longitude. This is just 373 miles (600 kilometers) from Curiosity’s landing site, Gale Crater.

    The landing ellipse was about 81 miles (130 kilometers) long, generally west to east, and about 17 miles (27 kilometers) wide, covering the area within which the spacecraft had about a 99 percent chance of landing when targeted for the center of the ellipse.

    InSight takes 360-panoramic images in all directions at this landing site. Scientists expected a flat surface, no hills nearby and few large rocks in view. That was based on high-resolution images taken from orbit as part of thorough evaluations for selecting the site.

    Selecting Where to Land

    Several workshops took place in 2013, 2014 and 2015, to evaluate 22 candidate landing ellipses and then four finalists. All 22 of those sites are in Elysium, which is one of only three areas on Mars that meet two of InSight's needs.

    One requirement was that the landing site must be close enough to the equator. This ensures that the lander's solar array can provide adequate power at all times of the year and the lander can stay warm: between 5 degrees north latitude and 3 degrees north latitude.

    The site's elevation must be low enough to have sufficient atmosphere above the site for a safe landing, because the spacecraft relies on the atmosphere for deceleration during descent.

    The High-Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter plays an important role in evaluating candidate landing sites on Mars. HiRISE took about 150 images of candidate InSight landing sites, covering nearly all of the ground of the final site.

    Landing Successfully on Mars

    Finalist Site for Next Landing on Mars
    Finalist Site for Next Landing on Mars: This map shows the single area under continuing evaluation as the InSight mission's Mars landing site, as of a year before the mission's May 2016 launch. The finalist ellipse marked is within the northern portion of flat-lying Elysium Planitia about four degrees north of Mars' equator.

    InSight's scientific success and safe landing depended on landing in a relatively flat area. It also depended on landing in an area where rocks are few in number. A slope too steep could foil the robotic arm's access to a sufficiently large work area. A sufficiently steep slope in the wrong direction could jeopardize how much power the solar arrays can produce. A large enough rock at the landing site could block one of the solar arrays from opening.

    The site evaluation also considered the subsurface structure. For mission success, InSight’s heat flow probe must be able to penetrate the ground in the lander's workspace. The probe was designed to burrow into soil (not rock) to a depth 10 to 16 feet (three to five meters). The Thermal Imaging System (THEMIS) on NASA's Mars Odyssey orbiter provided key evidence that the chosen landing site is suitable for burrowing. THEMIS observations can show how quickly the ground cools at night or warms up in sunlight. Solid rock changes temperature more slowly than softer ground.