About 31 million miles away from Earth, the Rosetta spacecraft is circling a rubber ducky-shaped comet and getting reading for touchdown. On November 12 at around 4 a.m. EST, the orbiter will release the Philae lander, which will become the first manmade object ever to touch down (or maybe crash) on a comet.
It will be a challenging landing. Comet 67P/Churyumov–Gerasimenko is small, with a diameter of about 3 miles by 2 miles, leaving little room for error. And it’s a lot weirder in shape than scientists ever imagined. The landing site is not flat, and it’s surrounded by cliffs and potentially hazardous boulders. Making matters more difficult, the spacecraft is so far away that the 28-minute communications delay means the whole ordeal will basically have to take place on autopilot.
Here’s how the historic landing is expected to go down:
1. Separation
The orbiter will swoop from its altitude of 18 miles down to 14 miles above the comet’s surface. From that height, it will maneuver into position above the landing site. When the time is right, the orbiter will open a hatch and activate two motors that will push the lander out in a sort of celestial birthing.
2. Descent
When it’s leaving the orbital womb, Philae will be traveling at about eight inches per second. After that, it won’t really be able to steer itself or control its speed—mission scientists just have to hope the orbiter had good aim. “We need a certain amount of luck to end up in a nice spot,” Paolo Ferri, head of mission operations, told the BBC.
The descent to the comet’s surface will take about seven hours, during which Philae will be taking pictures of the comet and orbiter, and sampling the dust, gas, and plasma around it.
3. Anchors Away
As it nears the surface, Philae’s legs will unfold from its body. Touchdown will take place at less than three feet per second, or about walking speed here on Earth. Then, because the comet’s gravity is so low, the lander will have to utilize a variety of mechanisms to anchor itself in. As it reaches the surface, thrusters will push the lander down as two harpoons will shoot out and dig into the icy dirt. Screws on the lander’s feet will then twist into the soil for additional safety.
4. Getting Down To Business
Once it’s secure, the first thing Philae will do is snap a panoramic picture of its surroundings and beam it back to Earth. Then the spacecraft’s real job begins. Over the course of six months or so, the lander will study the comet’s internal structure using radio waves, and it will drill down into the dirt to learn about its water and carbon content. And as the comet’s elliptical orbit brings it nearer to the Sun in the spring of 2015, Philae will measure the dust and ice that vaporize from the soil.
Landing on a comet is risky business, but the ultimate goal is pretty cool: Rosetta will help scientists learn more about what conditions were like when the solar system was forming, and whether or not comets could have seeded life on Earth.
