Learning about Mars

An international team of space researchers has learned more about the density of the Martian surface by analyzing data from the Mars InSight lander that was received during the Perseverance descent. In their paper published in the journal Nature Astronomy, the group describes their study of InSight seismic data when Perseverance threw heavy blocks during their descent.

 One of the ways that planetary scientists learn more about the composition of other planets is by studying seismic activity; waves of such activity can provide clues to the density of different parts of a planet.  In this new effort, the researchers noted that collecting seismic data from extraterrestrial events, such as asteroids striking the surface of a planet, is difficult because they are so random. But they also noted that the Perseverance mission offered a unique opportunity: As part of its descent earlier this year, the rover's landing craft dropped two blocks of tungsten, each weighing approximately 77.5 kg, to the surface. The blocks were dropped to help with the lift and drag ratio of the ship. Fortunately, the InSight probe (which has been on the surface since 2018) was located just 3,450 km east of where the blocks landed, a golden opportunity to learn more about the density of the Martian surface.The team also accessed Perseverance data to determine the altitude and velocity of the rocks as they fell, allowing them to calculate the force of the impacts and when they impacted. They were also able to observe the impact sites by accessing high-resolution images from orbiting spacecraft. Looking at the InSight data, the researchers found no evidence that the blocks smashed into the surface, suggesting that the surface was of such density that the seismic shapes created by the impact were silenced. They estimate that less than 3% of the energy from the blocks hitting the surface made its way to the material below, a figure that could be useful when trying to measure the impact of other space objects.  They note that a better understanding of such impacts could prove useful to engineers trying to build structures on Mars for later human habitation.