After completing a 300 million mile journey in space, touching down on the Martian surface, and taking a few days' break to primp itself and snap a few selfies, NASA's InSight lander has now completed yet another important milestone by placing its seismometer on the surface of the Red Planet. The sensor will collect a great portion of the mission's scientific data and will combine with a heat probe to investigate the internal structure of Mars, even registering much of the local "weather," from dust devils to meteorite strikes.
The SEIS instrument – short for "Seismic Experiment for Interior Structure" – is the first seismometer to be deployed to the surface of Mars in over 40 years. Its two predecessors were aboard each of the Viking landers (which landed in 1976), but they were unable to collect useful data because they were housed on the landers themselves, where their measurements were easily thrown off by vibrations caused by winds and the nearby equipment.
To circumvent the problem, this time around NASA designed a seismometer that could be manipulated by a mechanical arm and deposited directly on the Martian surface. The exact spot was carefully chosen after scientists back on Earth examined pictures of the terrain in the immediate surroundings, within the 5-ft (1.5 m) reach of the arm. This long-awaited step was successfully completed on December 19.
In early January, the mechanical arm will be deployed once more to place a protective cover which will shield the seismometer from wind interference. This will complete the deployment of the sensor, so that the valuable data collection may begin at last.
"Seismometer deployment is as important as landing InSight on Mars," said InSight Principal Investigator Bruce Banerdt. "The seismometer is the highest-priority instrument on InSight: We need it in order to complete about three-quarters of our science objectives."
Specifically, SEIS will be able to register seismic waves caused by "marsquakes," the impact from meteorite strikes (NASA expects to record up to 10 of them over the course of the mission), and, because of the extreme sensitivity of the instrument, even weather phenomena like dust devils, which are sometimes the cause of marsquakes.
By late January, the robotic arm will come to life once again to deploy a second instrument – an advanced heat probe – onto the surface. The probe will slowly and autonomously dig a few meters into the ground with a hammering motion. The vibrations generated by the burrowing process will then be picked up by SEIS and used to understand the structure of the subsurface.
NASA expects that the analysis of the seismic activity will produce reliable data on the inner composition of the Red Planet, providing useful insights into how this and other bodies in our solar system have formed.
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