It’s now more than a year since NASA’s InSight lander mission touched down on Mars on November 26, 2018. What lessons has the mission provided in its first year on the Red Planet? This week, NASA published a set of six papers – five in the journal Nature, one in Nature Geoscience – to reveal “a planet alive with quakes, dust devils and strange magnetic pulses”.
What is InSight
InSight is the first mission dedicated to looking deep beneath the Martian surface. Among its science tools are a seismometer for detecting quakes, sensors for gauging wind and air pressure, a magnetometer, and a heat flow probe designed to take the planet’s temperature.
The InSight mission is part of NASA’s Discovery Program. It is being supported by a number of European partners, which include France’s Centre National d’Études Spatiales (CNES), the German Aerospace Center (DLR) and the United Kingdom Space Agency (UKSA).
Mars trembles more often than expected, but also more mildly. This emerged from readings of the ultra-sensitive seismometer, called the Seismic Experiment for Interior Structure (SEIS). The instrument enables scientists to “hear” multiple trembling events from hundreds to thousands of miles away.
Mars doesn’t have tectonic plates like Earth, but it does have volcanically active regions that can cause rumbles. SEIS has found more than 450 seismic signals to date, the majority of which are believed to be quakes (as opposed to data noise created by environmental factors, like wind). The largest quake was just about magnitude 4.0 in size.
Seismic waves are affected by the materials they move through. As such, they help scientists study the composition of the planet’s inner structure. Mars can help the team better understand how all rocky planets — including Earth — first formed.
The surface: magentism
Billions of years ago, Mars had a magnetic field. Although it is no longer present, it left behind what NASA describes as “ghosts” – magnetised rocks that are now between 61 m to several km below ground. InSight is equipped with a magnetometer, which has detected magnetic signals.
At a Martian site called Homestead hollow, the magnetic signals are 10 times stronger than what was predicted earlier (based on data from orbiting spacecraft). Because InSight’s measurements are more local, they ate more precise.
At InSight’s location, most surface rocks are too young to have been magnetised by the former magnetic field. “This magnetism must be coming from ancient rocks underground,” Catherine Johnson, planetary scientist with the University of British Columbia and the Planetary Science Institute, said in a statement issued by NASA. Scientists are now using these data and what was previously known to understand the magnetised layers below InSight.
In addition, scientists on Earth are intrigued by how these Martian signals change over time. The measurements vary by day and night; they also tend to pulse around midnight. Theories are still being formed as to what causes such changes.
In the wind: dust devils
InSight measures wind speed, direction and air pressure nearly continuously. Weather sensors have detected thousands of passing whirlwinds, which are called dust devils when they pick up grit and become visible. The site has more whirlwinds than any other place where a landing has been made on Mars while carrying weather sensors.
Despite all that activity in the wind and frequent imaging, InSight’s cameras have yet to see dust devils. But SEIS can feel these whirlwinds pulling on the surface. “Whirlwinds are perfect for subsurface seismic exploration,” said Philippe Lognonné of Institut de Physique du Globe de Paris (IPGP), principal investigator of SEIS.
The core: still to come
InSight has two radios. One is for regularly sending and receiving data. The other radio, which is more powerful, is designed to measure the “wobble” of Mars as it spins. This X-band radio, also known as the Rotation and Interior Structure Experiment (RISE), can eventually reveal whether the planet’s core is solid or liquid. A solid core would cause Mars to wobble less than a liquid one would.
This first year of data is just a start, NASA said in the statement. When it is two years on Earth, Mars will have completed one year. A full Martian year will give scientists a much better idea of the size and speed of the planet’s wobble, NASA said.