On Wednesday November 12 at 17:30 Israel time, the Philae lander will land on comet Churyumov-Gerasimenko – the first ever landing on a comet. The lander will be anchored to the surface by harpoons and screws that will penetrate the comet’s icy surface. This anchor is necessary to hold the lander on the brittle ice surface of the comet’s exterior.
Twenty-five years ago a group of comet researchers which included Prof. Akiva Bar-Nun of the Department of Geosciences at Tel Aviv University developed the idea of flying the Rosetta spacecraft for a year alongside the comet’s nucleus, and to land the Philae lander on its surface, in order to examine the strength and composition of the ice.
Up till now the Rosina Group, in which Prof. Bar-Nun is a member, has received findings indicating that the comet was created at a temperature of minus 250° Celsius at the edge of the solar system. An additional finding diminishes the importance of comets in bringing water and organic material to the young planet Earth, in contrast with previous theories.
“Molecular Nitrogen (N2) is the greatest discovery we’ve made up till now,” says Prof. Bar-Nun. This was a ‘bombshell’ because to date we haven’t observed nitrogen on comets. Now we expect to find noble gases like Neon, Argon, Krypton and Xenon. As they get closer – the comet and the Rosetta spacecraft – to the sun, the comet heats up and becomes more and more active, which enables us to discover substances in very small concentrations.”
The Rosetta spacecraft of the European Space Agency was launched in 2004. On August 6, 2014 the spacecraft entered into an orbit around the comet, and on November 12 the Philae lander will be deployed from the spacecraft and will attempt to land on the comet’s surface. Philae should deploy at 10:35 Israel time and, after traveling for 22 kilometers, will land on the comet at 17:30. Messages from the distant spacecraft will reach earth 28 minutes later, so that at 18:00 Israel time we will know whether Philae was able to land and anchor on the ice surface.
To date, all spacecraft have passed near comets – but none of them has yet landed on one,” said Prof. Bar-Nun. 25 years ago we thought about landing on a comet, drilling down and bringing some material back to earth. The problem was that we didn’t know at the time the mechanical strength of the surface. The engineers told us: Guys, first go to the comet and measure it, and then come back to us. You have to understand that a comet has very little gravitational pull so that you have to hold on to the surface by force. But the ice surface is not very dense, like snow that has fallen and is still very soft.”
This research is funded in the last four years by a grant from the Israel Space Agency, through the Ministry of Science.