How to Land a Spaceship on a Comet in Eight Steps

If successful, it would be scientists' first-ever landing and a major boon to space explorers. If not, it could be a mighty big bang.

Rosetta will orbit 67P/Churyumov-Gerasimenko before sending a probe to land on it. (National Journal)

Scientists are trying to land a probe on a comet millions of miles from Earth that is traveling at roughly 10 times the speed of a bullet. Here's their plan:

Step 1: Wake up your spaceship. The Rosetta craft, hibernating for nearly three years, was 500 million miles from the sun — way out past Jupiter. Now, it's closer to 400 million miles away, and near enough to pick up the solar power it needs to keep itself going. On Monday, scientists pulled Rosetta out of its slumber.

Comets are considered the "primitive building blocks of the solar system," yet much is still not known about them. According to NASA's Sam Gulkis, the mission will "create the most complete picture of a comet to date, telling us how the comet works, what it is made of, and what it can tell us about the origins of the solar system."

Step 2: Find your target. By May, when Rosetta is 1.2 million miles from the approaching comet, the European Space Agency expects it to start sending back images of the 67P/Churyumov-Gerasimenko, a two-and-a-half-mile-wide comet that's about to enter our solar system. As it gets closer, NASA says, it will "transform from a small, frozen world into a roiling mass of ice and dust, complete with surface eruptions, mini-earthquakes, basketball-sized, fluffy ice particles, and spewing jets of carbon dioxide and cyanide."

Step 3: Get in position. At the end of May, Rosetta will begin lining itself up for a rendezvous with the 67P. A comet landing has never been done before — all previous six comet encounters were in the form of brief flybys, two of them by Rosetta. But ESA, with help from some NASA instruments, thinks it's ready to give it a try.

Step 4: Catch your comet. The fateful meeting is expected to take place in August. If all goes well, Rosetta will park itself in orbit around 67P and follow it in and out of the solar system for 16 months.

Step 5: Find out what makes your comet tick. As Rosetta orbits the comet, its three NASA-provided instruments will come into play. A microwave instrument will sense temperature and chemicals, as well as gaseous activity. Alice, a spectrometer, will measure the ultraviolet portion of the spectrum to test for water, carbon monoxide, and carbon dioxide. And an ion and electron sensor will help define the comet's plasma atmosphere.

Step 6: Prepare for landing. The real moment of truth will come Nov. 11. That's when the tiny Philae lander, honing in on a landing spot chosen by Rosetta's mapping, will try to touch down on the comet. The 220-pound probe will deploy ice screws and harpoons as it hits the surface, because 67P's minimal gravity is not enough to keep it anchored.

Step 7: More testing — up close and personal this time. If the landing goes well, Philae will start sending back high-resolution pictures. Then it will begin analyzing ice and material samples, drilling up to nine inches below the surface.

Step 8: Stick around, enjoy the ride. Philae's job complete, Rosetta will stay alongside 67P as it nears the sun, watching its ice react as the comet heats up. It will eventually get around 115 million miles from the sun, "roughly between the orbits of Earth and Mars."