Here is the heat probe from NASA’s InSight land – nicknamed “the mole” – on October 3, 2020, when the spiky mole was still trying to dig into the red Martian soil. The copper-colored ribbon attached to the mole has sensors to measure the heat flow of the planet. Now NASA engineers have halted this part of the mission. Image via NASA / JPL-Caltech.
One important aspect of NASA’s InSight mission to Mars unfortunately came to an end last week. NASA announced that InSight’s HP3 heat probe – even the mole – could not get the friction it needed to dig so deep into the surface of Mars. Now, mission engineers have put an end to efforts, according to NASA, to sink the probe deeper into the ground. However, there is also good news. The mission has received an expansion, giving more time on Mars’ surface to perform its other tasks.
The mole – officially known as the Heat Flow and Physical Properties package – is designed to dig up to 5 meters. The aim was to measure the internal temperature of Mars, with important indications of how geologically active Mars is still and how much heat it still retains in its interior.
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The problem was that the mole needed friction from the surrounding soil to be able to dig deeper. It appears that the ground in that part of Mars was more lumpy than expected, which means less friction. The mole would penetrate a few inches or so, less than an inch, and then it would tend to jump up again. Eventually, the mission team tried to push the mole further down with the shovel on the lander’s robotic arm. Soil would be scraped on the mole, and then the spoon would be used to stamp it off with a hammer blow, which hopefully provides more friction. It worked to some extent for a while, but was still not enough to make the mole dig further.
By January 9, 2021, more than 500 such hammer blows had been carried out, to no avail. At that point, the mission team ended the effort.
This is unfortunate, but – as you can imagine – there are often unexpected problems when exploring worlds hundreds of millions of miles away. As Tilman Spohn of the German Aerospace Center (DLR), who built the mole, said:
We have given everything we have, but Mars and our heroic mole remain incompatible. Fortunately, we have learned a lot that will benefit future missions that try to dig into the underground.
The mission team used the shovel at the end of the robot arm to drive the heat probe deeper into the ground. However, the attempts were unsuccessful due to the lack of friction in the ground due to clumsiness. Image via NASA / JPL-Caltech.
Artist’s concept of NASA’s InSight lander on Mars, with a view of the subsurface. Image via PGP / Nicolas Sarter / JPL-Caltech.
Other landers and robbers used spoons to dig into the surface layers of the ground to get samples, but the mole from InSight was meant to dig significantly deeper. The failure to dig deep enough is disappointing, but it was certainly not a lack of trying and is still a success in other ways. As Thomas Zurbuchen, co-administrator of science at NASA, said:
We are so proud of our team that worked hard to get InSight’s mole deeper into the planet. It was amazing to see them dissolve millions of miles away. That’s why we’re taking a risk at NASA, and we need to shift the boundaries of technology to learn what works and what doesn’t. In that sense, we were successful: we learned a lot that would benefit future missions to Mars and elsewhere, and we thank our German partners of DLR for providing this tool and for their cooperation.
What went wrong then?
The awkwardness of the ground was surprising, as the testing of the instrument on Earth was based on the properties of the Martian soil seen by previous missions to Mars. But the ground at InSight’s landing site, in Elysium Planitia, appears to be different from any other landing site. According to Troy Hudson, a scientist and engineer at NASA’s Jet Propulsion Laboratory (JPL):
The mole is a device without heritage. What we tried to do – to dig so deep with a small device – is unprecedented. The chance to take it to the end is the biggest reward.
InSight has many different scientific tools. The heat flow probe, on the right, was supposed to protrude about five feet into the ground. Image via NASA / JPL-Caltech.
Diagram of the heat flow probe. Image via DLR / InSight Project / Ruimtevlieg 101.com.
However, not everything is lost. The setback gave the mission team more experience with the robotic arm, as well as the chance to learn more about the land at this location. What makes it more lumpy?
Another task in the near future will be to use the robotic arm to bury the binder that connects the seismometer instrument – the Seismic Experiment for Indoor Structure (SEIS) – to the lander. It is hoped that this will reduce the cracking and popping sounds heard in the seismic data due to temperature changes.
SEIS takes the “pulse” of Mars, listens to surface seismic activity, and has so far recorded more than 480 marsquakes. By far most are very small, but they tell scientists how active Mars is below the surface. It appears so far somewhere between the earth and the moon. Some of the seismic activity that InSight has detected comes from regions with still active faults and ancient volcanoes, suggesting that Mars may still be volcanically active to some extent, at least below the surface.
The lander itself still has excellent health, which is good news, and the mission has been extended for another two years until December 2022. This means that there is much more science that can be done with all the other tools of InSight.
InSight’s mission is primarily to study the interior of Mars and determine if the planet is still geologically active. Image via NASA / JPL-Caltech.
InSight’s overall mission is to study the interior of Mars, to determine how geologically active the planet is still, and how it has formed and changed over the past few years. A radio experiment on board called Rotation and Interior Structure Experiment (RISE) was designed to find out if Mars’ core is still liquid or solid, and what its overall composition is, including iron.
InSight also monitors the weather of Mars on the surface, with some of the most advanced weather sensors ever sent to the planet. The Curiosity rover also monitors the atmosphere and the weather, just like the Perseverance Rover when it lands next month, on February 18th. All three will together create the first meteorological network on another planet, another great achievement.
The mole may not be digging anymore, but the mission is far from over, with still a lot of good science!
In short, the mission team for NASA’s InSight lander on Mars has put off further attempts to dig deep into the ground with the heat probe instrument called ‘the mole’. However, the rest of the mission will continue with an extension until December 2022.
Via JPL
