Saving the World by Harpooning a Comet

Comets are thought to be the perfect specimens to study the primordial stuff that created our solar system. These icy objects can speed through the inner solar system at up to 150,000 miles per hour after making the long journey from the outer reaches of our Sun’s gravitational influence. As you might imagine, collecting samples from these fleeting visitors can be very difficult. Landing on one is probably out of the question considering their uneven surfaces; however, NASA scientists have come up with a clever idea to get around this difficulty. Instead of landing they will have a craft “hover” over the surface of the comet and fire a harpoon to rapidly collect samples from different locations around the comet.

Currently in testing, the firing device is positioned to fire vertically downward into a bucket of target material. It cannot be positioned upward because if it accidentally fires, it could potentially launch a test harpoon tip about a mile! An mechanical winch pulls the bow back to generate enough force to fire the harpoons up to 100 feet per second. The test material is a mix of sand, salt, pebbles, but nobody is sure what they will encounter on the comet itself. It could be a combination of things like the test bed, or it could be mostly dust or even solid rock. This is the tricky part of the harpoon engineering. Most likely the comet will be composed differently in different areas, so the design must be capable of penetrating different types of materials.

Also in testing, the harpoon tip must contain a hollow chamber to store the samples collected. When fired, the chamber has to remain open, but then close and detach from the tip in order to return to the spacecraft. This has to be done in a small cross-section and succeed for a wide range of materials. Because no team has done this before, the scientists are still working on very basic questions like how much powder charge you need so that the harpoon doesn’t bounce off the surface, but also doesn’t fire right through the comet. The device also needs to penetrate deep enough to get a good sample, but then return to the spacecraft and not get lodged in the comet.

Harpoon chamber

The harpoon chamber in testing to collect samples from inside a comet (NASA)

If the mission is successful, the goal is to study the samples to look for biomolecules that could have assisted in the origin of life. NASA’s Stardust mission revealed that comet Wild 2 contained amino acids which are the building blocks of proteins. These findings support the theory that comets contain a sort of “kit’ that contain the parts necessary in creating life on Earth through delivery. While comets may be responsible for the beginning of life on Earth, they might also be responsible for major extinctions. By analyzing how comets are structured, it may be possible to devise a defense strategy should one come knocking on our door. Some strategies suggested include detonating a large, probably nuclear, explosion near the comet to deflect it out of harms way. However, depending on the comet’s composition, this may turn a large impact into lots of slightly smaller impacts. Sort-of like getting hit with a shotgun blast rather than a rifle bullet. Neither is very pleasant. Other methods include attaching a type of solar powered sail or attaching a rocket to push it out of the way. Missions like this one in testing may allow us to save the world, who knew!

About Dan Gifford

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