New research suggests an impact recently rattled Mars deeper than thought.
Something really rang the Red Planet’s bell. Research involving two NASA missions—the Mars Reconnaissance Orbiter, and the late InSight lander—has shed light on meteorite impacts and the seismic signals they produce. In a crucial finding, these signals may penetrate deeper inside Mars than previously thought. This could change how we view the interior of Mars itself.
The study comes from two papers published this week in the journal of Geophysical Research Letters. The primary data comes from NASA’s InSight mission, the first dedicated geodesy mission to Mars. Insight landed in the Elysium Planitia region of Mars on November 26th, 2018, and carried the first ever dedicated seismometer to the Red Planet. During its four years of operation, Insight detected over 1,300 ‘marsquakes,’ until the mission’s end in 2022. Most were due to geologic activity, while a few were due to distant meteorite impacts. Occasionally, InSight would even see ‘land tides’ due to the passage of the moon Phobos overhead.
A Distant Mars Impact
As on Earth, the detection of seismic waves gives us the opportunity to probe the interior of Mars, providing clues as to the density, depth and thickness of the crust, mantle and core. To be sure, impacts have been correlated to seismic waves captured by InSight in the past: a fresh crater seen by NASA’s Mars Reconnaissance Orbiter (MRO) in 2022 was correlated to an impact in the Amazonis Planitia region. But this was the first time an impact in the quake-prone Cerberus Fossae area was linked to InSight detections. The find is especially intriguing, as the area is quarter of a world away from the InSight landing site, at 1,640 kilometers (1,019 miles) distant.
The discovery of the 21.5-meter (71 foot) crater about the length of a semi-truck immediately presented scientists with a mystery. The smoking gun impact crater was more distant than thought. Typically, the Martian crust was thought to have a dampening effect on distant impacts… this meant that the impact generated waves that took a more direct route via a ‘seismic highway,’ through the deeper mantle of the planet itself.
A New View of the Interior of Mars?
This discovery has key implications for what we generally think about the interior of Mars, implying that our understanding and model for the planet’s interior may be due for an overhaul.
“Composition of the crust and how seismic waves from impacts travel through them is one factor,” Andrew Good (NASA-JPL) told Universe Today. “No current plans for follow-on seismometers on Mars, but there is a seismometer planned for the Moon in the near future,” says Good, in reference to the Farside Seismic Suite planned for 2026.
Just how researchers imaged the tiny crater is the amazing second part of the story. NASA’s venerable MRO generates tens of thousands of images of the surface of Mars, mainly via the spacecraft’s onboard Context Camera. For years, researchers have used a machine learning algorithm to sift through the images, looking for fresh impact sites that do not appear in previous frames. These areas are in turn flagged for closer scrutiny with the mission’s 0.5-meter High-Resolution Imaging Science Experiment (HiRISE) camera. The AI program was developed by NASA’s Jet Propulsion Laboratory.
To date, the team has found 123 new craters within 3,000 kilometers (1,864 miles) of the InSight landing site, 49 of which (including the Cerberus Fossae impact) are potential matches with InSight seismology data.
“Done manually, this would be years of work,” says InSight team member Valentin Bickel (University of Bern, Switzerland) in a recent press release. “Using this tool, we went from tens of thousands of images to just a handful in a matter of days.”
InSight’s Legacy
InSight provided a wealth of seismology and geological information about Mars. The Seismic Experiment for Interior Structure (SEIS) instrument worked as planned. The Heat Flow and Physical Properties Package (HP^3) failed, however, to reach its target depth for returning useful science about the planet’s interior. Unfortunately, no dedicated follow on geology mission is set to head to Mars. This sort of exciting science will probably have to wait until the hoped for crewed missions of the 2030s.
InSight was a collaborative effort between NASA, the German Space Agency (DLR) and the French Space Agency (CNES). Other international partners also participated in the ground-breaking mission.
Still, it’s great to see missions like InSight still generating scientific results, long after they’ve fallen silent.