There’s some happy news to report from the Red Planet, as the stubborn Mars InSight heat probe, known as “the mole,” is now completely buried. It’s an encouraging development, as the surrounding dirt could coax the device into drilling deeper through the Martian crust.
The ongoing saga of the InSight lander’s Heat Flow and Physical Properties Package has taken an important turn, or at least we hope. The self-hammering drill, built by the German space agency (DLR) and operated by NASA’s Jet Propulsion Laboratory, is now completely obscured by red Martian dirt—a sign that it may soon be able to dig properly, since it needs friction to move downwards. Up until this point, it’s mostly been bouncing up and down like a useless pogo stick.
The purpose of the mole, as the cool kids call it, is to take temperature readings beneath the Martian crust, at a maximum depth of 10 feet (3 meters). But this device has proven to be the most frustrating aspect of the InSight mission, which began in November 2018 when the lander arrived at Elysium Planitia. Until recently, the 16-inch-long (40-centimeter) probe could barely clear the surface, and at one particularly distressing point—around a year ago at this time—Mars rejected the drill, spitting it back out onto the surface.
Now, it’s not mole that’s uncooperative, but rather the Martian dirt. The mole’s self-hammering action is causing the dirt to clump together, forming a gap around the device instead of collapsing around it. Unfortunately, NASA can’t simply pick up the mole and try digging elsewhere: the probe doesn’t have a “grapple point” that can be grasped by InSight’s robotic arm.
Starting last year, to prevent the mole from moving in the wrong direction, mission planners used InSight’s scoop to try to pin the probe to the bottom of the pit and keep it in the ground. This worked for a bit, but NASA hit a snag in July when the mole stopped descending. The team blamed duricrust—a cement-like mixture in which granules stick together—for the interruption. NASA hit the pause button at this point because the InSight arm was required for other tasks, but it’s now back on mole detail.
As NASA reports, the mole is now fully buried in the Martian regolith and out of sight. All that’s visible now is the ribbon cable sticking out of the ground (the cable is laden with temperature sensors designed to measure the heat flow beneath the surface).
“I’m very glad we were able to recover from the unexpected ‘pop-out’ event we experienced and get the mole deeper than it’s ever been,” explained Troy Hudson, the JPL engineer who’s leading this effort, in the NASA statement.
Hey, he said “unexpected ‘pop-out’ event,” not me. I’m simply the messenger.
Anyhoo, the next step will be for the arm, with its handy scoop, to pile more dirt on top and pack it down nice and tight. NASA says this will take months, and it won’t be hammer-time for the probe until early 2021. Hudson wants to “make sure there’s enough soil on top of the mole to enable it to dig on its own without any assistance from the arm,” he said.
Sounds like the InSight team has some tedious but important work ahead of them. That the probe is now completely buried is encouraging news, but there’s still no guarantee that NASA’s strategy will work. As mentioned, the team appears to be dealing with less-than-ideal dirt, and the hammering action could continue to create pockets inside the hole, resulting in the loss of friction. Let’s hope I’m wrong, and that we’ll soon see some temperature readings of the Red Planet at depth.