Martian Stratigraphy & the InSight Lander

In 2018, our global society had a new milestone to be proud of. The InSight Lander, a machine spawned as the result of collaboration among some of the brightest minds across the globe, had successfully landed on Mars and was operating mostly as intended. This machine, Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight), was a practically immobile device that was intended to get a ‘physical checkup’ on Mars. It carried several instruments, including SEIS, HP3, and RISE. SEIS was a seismometer that could detect vibrations on the planet. HP3 was a thermometer intended to study the Martian geothermal gradient. RISE was a positioning device similar to GPS on Earth, intended to get a sense of Mars’ size given its movement behaviors as it orbits the Sun.

Shortly prior to the lander’s departure from Earth, NASA in collaboration with many global scientists in the InSight Participating Scientist Program was busy determining an optimal landing location. Eventually, a spot on Mars known as western Elysium Planitia was chosen, and a ‘landing ellipse’ was drawn to delineate the general zone where the lander should be placed.

Map of Mars circa 2018, projected to a 2D plane. General location of western Elysium Planitia on right.

Zoomed-in view of portion of western Elysium Planitia representing the landing ellipse location with regard to Elysium Mons. Basemap is a colored digital elevation model for the region.

A lot of planning went into the placement of this ellipse. Among the list of variables influencing this decision, was the question of the surficial composition in this zone. The team had relied on images taken at oblique angles from the Mars Reconnaissance Orbiter to view stratigraphy, or ‘layers’, of rock and sediment. Using some creativity, they were able to generally estimate the composition of these layers by peering into features like craters, fissures, and channels. Among these features were the fissure sets of Hephaestus Fossae and Elysium Fossae bounding Elysium Mons.