It’s been a long road for InSight’s Mole. InSight landed on Mars almost two years ago, in November 2018. While other lander spacecraft work well and return scientific data, the Mole is struggling to make its way to the planet’s surface.
After a lot of hard work and a lot of patience, the Mole finally managed to bury himself completely in the Marian regolith.
But the drama is not over yet.
The mole is a 16-inch heating probe that plunges deep into the surface. Its maximum depth is 5 meters (16 feet) below the surface and this is its ideal working depth. But it can also collect useful scientific data at shallower depths of about 3 meters (10 feet). As it is now, the mole is nowhere deep enough to engage in any science.
But two years later, it̵
The real name of the mole is the package for heat flow and physical properties or HP3. It is designed to measure the heat coming from inside Mars. The strap that connects it to the InSight trigger contains heat sensors along its length. InSight means “Interior surveys using seismic surveys, geodesy and heat transport”. The heat transfer part of the mission is the work of the mole.
Ever since the tool was deployed, it has been facing problems. The mole penetrates, digging slowly into the ground. But this knocking motion relies on the friction between the mole and the walls of the hole. Without this friction, the tool simply bounces back out of the hole.
The problem is in what is called a duricrus. This is a hardened surface layer that forms in dry areas. And Mars is definitely waterless. The duct around the mole prevents the soil from falling into the mole hole while knocking, and deprives the tool of the necessary friction to pierce it on Mars.
While InSight is primarily a NASA mission, Mole was designed and built by DLR (German Aerospace Center). They worked with NASA’s JPL, which has an engineering version of the Mole in a test bed. There they tried to overcome these challenges.
They tried to use the spoon at the end of the InSight tool’s arm to apply lateral pressure to the Mole, hoping to provide the necessary friction. They tried to push the Mole as well, while carefully avoiding the sensitive connection. And they tried to scoop up bulk material with a spoon and deposit it in the Mole’s hole.
Today, NASA announced that the Mole is finally completely buried in the dirt. This is a kind of victory, but there is still a long way to go. Now that he’s buried, the InSight team will continue to pull more finger on the tool and drive it in before resuming the blows.
But all this takes time.
“I’m very happy that we were able to recover from the unexpected” pop-up “we experienced and make the mole deeper than it ever was,” said Troy Hudson, a scientist and engineer at NASA’s Jet Propulsion Laboratory. , supervised the work to make the mole dig. “But we are not quite ready. “We want to make sure he has enough soil on the tip of the mole to dig on his own, without any help from his hand,” Hudson said in a press release.
It will take months for the soil to be shoveled and compacted. NASA says the hammering operation is unlikely to resume until January 2021. Part of what is hampering the operation is the accumulation of dust on InSight’s solar panels. This reduces the power available for the entire mission.
Tillman Spon is the scientific director of the Mole at DLR. He writes a blog about efforts to make the mole work. In today’s recording on October 16, 2020, Spohn talks about the next steps and how they work for the next “Free Mole Test”. The free mole test is when they let the mole try to make its way under the surface without the help of a spoon.
“After some discussion about the next steps, we decided that on Saturday, October 17 (Sol 659), two parallel spoon movements should take place,” he wrote.
“Thermal conductivity measurements will then be made, which should also give us indirect indications of filling,” Spohn wrote. “Then the filling will be pressed to compress the sand and press the Mole. Depending on the backfill result, further actions will be planned to fill the pit before further knocking and another free bin test will be performed later. “
On Earth, it would be easy to use a drill to penetrate below the surface. But drills are heavy, require a lot of power, and need stability to keep them from spinning instead of drilling. This is simply not possible on Mars. The drill will weigh too much and require much more power than the mole. The mole is only 1 inch (2.7 centimeters) in diameter and about 16 inches (40 centimeters) long. It had to be light enough and small enough to fit the limits of the mission.
We hope that the mole will eventually reach its working depth. Meanwhile, other InSight tools work and return data. Thanks to SEIS (Seismic Experiment for Internal Structure), we know that Mars is a seismically active planet.
But without the mole and its heat transfer readings, the InSight will never fulfill its mission.