Around 2014, one of those orbiting comets will come close enough for a real grab at its contents. Hovering above the target comet, sub-surface samples could be precisely taken from even the most forbidding area of the body. NASA at Goddard Space Flight Center in Greenbelt, Maryland, are just beginning to improve on the present designs for actually landing and attaching to the almost gravity-free comet. "A spacecraft wouldn't actually land on a comet; it would have to attach itself somehow, probably with some kind of harpoon. So we figured if you have to use a harpoon anyway, you might as well get it to collect your sample," says Dr. Joseph Nuth, a lead scientist on this project.
The harpoon is to be fired from a ballista (shadows of ancient Rome) while a winch directs the force to be applied to the sampling attempt. The surface could be soft and fluffy or alternatively ice mixed with pebbles or solid rock. Obviously, choices will have to be made during the sample procedure. "One of the most inspiring reasons to go through the trouble and expense of collecting a comet sample is to get a look at the 'primordial ooze' - bio-molecules in comets that may have assisted the origin of life," says Donald Wegel, lead engineer at NASA Goddard. Comets are frozen chunks of ice and dust left over from our solar system's formation. As such, scientists want a closer look at them for clues to the origin of planets and ultimately, ourselves.
Scientists at the Goddard Astrobiology Analytical Laboratory have found amino acids in samples of comet Wild 2 from NASA's Stardust mission. That led to the recent development of comet collecting apparatus. The "origin of life" enthusiasts are joined however by the comet collision worriers, who are at pains to point out we can't just shoot them down! If Earth impacts a comet, we need to know how best to deal with specific impact threats and hopefully deflect them in an appropriate way. Let's hope it's one of those fluffy, soft and cuddly comets that hits us next.
Multiple sample collection from opening chambers which then clam up tight are also being developed for the harpoon's head.
This is a demonstration of the sample collection chamber:
Credit: NASA/Rob Andreoli
The European Space Agency is sending a mission called Rosetta that will use a harpoon to grapple a probe named Philae to the surface of comet "67P/Churyumov-Gerasimenko" in 2014 so that a suite of instruments can analyze the regolith. [NB. A regolith is a blanket of soil, broken rocks, dust, etc., on a solar body such as a comet.] "The Rosetta harpoon is an ingenious design, but it does not collect a sample," says Dr. Wegel. He hopes to cooperate in the ESA mission and include one of his sample-collecting cartridges. Perhaps a little more cooperation would save a lot of investment.
This video describes an artist's concept of a potential future comet sample return mission using a harpoon. (Credit: NASA's Goddard Space Flight Center)