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Moon and Mars are tough places to drill

NASA's InSight mole has unexpectedly popped out of its hole

NASA's InSight mole has unexpectedly popped out of its hole

In this image from Oct. 26, 2019, NASA's InSight's heat probe, or "mole," is seen after backing about halfway out of the hole it had burrowed. (NASA/JPL-Caltech)

A drill that has been stuck in Martian ground since last February has unexpectedly backed halfway out of the ground after unsuccessfully attempting to go deep. It turns out the soil on Mars is harder than scientists expected, much like what happened 50 years ago when astronauts tried to drill on the moon. 

The InSight mission to Mars landed on the red planet Nov. 26, 2018. Unlike earlier missions such as the Curiosity rover, which drives around taking images of the landscape and conducting chemical experiments on surface rocks, the main objective of InSight, which stands for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (where do they come up with these names?) is designed to find out what Mars is like on the inside. So rather than wheels for mobility, the spacecraft sits quietly in one spot to listen for activity coming from the inside of the planet. 

A seismometer placed on the ground has already detected "marsquakes," while a drill, or more accurately, a mole is designed to dig down several metres into the ground to measure the heat flowing out of the planet. This will give an idea of how hot the planet is deep down and whether it has a molten core as the Earth does.

Mole got stuck 

Unfortunately, the mole only managed to penetrate 30 centimetres into the soil before it stopped and became stuck. The mole uses an internal hammer to pound its way into the ground rather than a screw-style auger. But that technique requires friction from the soil so the mole doesn't just bounce in one spot.

Either it ran into a rock, the friction was not adequate or the ground is simply too hard, but the mole remained stubbornly stuck barely below the surface.

Recently, engineers used a robotic arm on the lander to gently press down on the top of the mole to help it burrow, but that did not make too much of a difference. Now that the reluctant mole has partially popped back out of the ground, scientists are trying to figure out what to do next.

Unknowns when drilling into alien worlds

This problem of drilling into an alien world for the first time was also encountered by the astronauts on Apollo 15 who sunk a heat probe into the moon where it got stuck, making it very difficult to pull out.  

In both cases of the moon and Mars, scientists expected the alien soils to be looser and softer than they turned out to be.

Apollo 15 astronaut Dave Scott prepares the lunar drill (NASA)

In fact, some scientists had suggested the moon would be covered in so much dust that any spacecraft attempting to land there would be completely buried. Thankfully a robotic spacecraft called Surveyor made a soft landing before the human missions and proved the ground was indeed solid with just a thin layer of dust, and strong enough to support astronauts.

The drilling problems on other worlds underlines how, even after half a century of leaving the Earth, we are still in the exploration phase of space. Our robotic probes are literally going where no one has gone before. And when troubles such as a stuck drill or probe happen, it is not a failure because we learn something new about those alien worlds, and are reminded once again that space exploration is hard... in every sense.

About the Author

Bob McDonald is the host of CBC Radio's award-winning weekly science program, Quirks & Quarks. He is also a science commentator for CBC News Network and CBC-TV's The National. He has received 12 honorary degrees and is an Officer of the Order of Canada.