A decade ago the European Space Agency spent 1 Billion Euros designing and launching the Rosetta probe with the intention of pursuing and eventually flying in formation with a comet with the ultimate goal to land on the comet.
We actually know almost as much about some planets orbiting other stars as we do about comets. There are theories, but we don’t even know for certain where comets originate. Until someone actually samples the surface of a comet all we will have are theories.
The ESA’s probe finally caught up with comet 67P/Churyumov-Gerasimenko early this August.
The comet is moving very fast, so fast no booster we have could catch it. Gravity boosts by four planetary passes were needed move the probe fast enough to keep up with the comet. This is the famous slingshot maneuver well known to science fiction fans, but it is actually a real process.
The mission will end December 2015 as the comet moves away from the sun after its August 2015 closest approach to the sun.
Today the ESA lander team narrowed the landing site to two choices, so what is happening now is that the ESA team is looking at the comet carefully trying to select the final landing point for Rosetta’s 100 kg Philae lander.
Landing on a small comet (or asteroid) isn’t as simple as might be thought. First, the comet is rotating, but the biggest problem is that there is virtually zero gravity – about 100,000 times less than earth surface gravity.
If the surface is hard (and we know it is) any attempt to land would result in the lander simply bouncing off back into space.
The designers hope they have overcome this by having harpoons ready to fire into the surface to anchor the lander. Of course this depends on whether the theories of what makes up the surface is correct.
If, as thought, comets are actually the remnant of material which built the planets and satellites of the solar system, the data from the Rosetta mission alone will tell us more about the composition of comets and the early solar system than all the information we have to date.
The lander uses ten on board instruments to drill down a foot under the surface for microscopic examination of the comet material, the lander will also use spectrometers, determine material density, texture, thermal properties and more.
For more information, check out my article in this month’s issue of Perihelionsf.com
