ESA: Philae probe landing on 67/P Churyumov-Gerasimenko comet next autumn

Touch down: This is what it could look like when the three-legged Philae lander touches down on the surface of the Churyumov-Gerasimenko comet in November. Credit: ESA/ATG medialab

In the coming autumn, the Philae probe is expected land on the nucleus of the 67/P Churyumov-Gerasimenko comet, which is a mere four kilometres in diameter.

Scientists from the Max Planck Institute for Solar System Research want to analyse the primeval building materials of the planets on site for the first time.

The list of celestial bodies that have already welcomed messengers from Earth is short. Our Moon is at the top as the place of the first manned landing.

Then come Venus and Mars and Europeans shouldn't forget Saturn's moon Titan, on whose exotic surface an ESA probe landed some time ago. Finally, there are the two planetoids Eros and Itokawa. That's it.

If everything goes according to plan this November, however, European space travel could again make history: the European Rosetta mission includes the landing on the nucleus of a comet.

Scientists from the Max Planck Institute for Solar System Research in Katlenburg-Lindau are playing a decisive role in the distant on-site inspection.

Philae, the lander, weighs around 100 kilogrammes and is the spacecraft intended to successfully perform this daring feat on 67/P Churyumov-Gerasimenko.

Hermann Böhnhardt

"We'll not only be exploring the comet for several months from an orbit, we want ground truth," says Hermann Böhnhardt.

Used here, ground truth means, in specialist terms: The observations of the Rosetta orbiter as it flies by are to be confirmed by measurements on the surface.

Max Planck researcher Böhnhardt is Rosetta's project scientist for the Philae lander.

The combination of these two probes makes it possible to carry out unique experiments, such as CONSERT (COmet Nucleus Sounding Experiment by Radiowave Transmission).

Its methodology is similar to a tomography examination, although the patient in this case is a comet's nucleus.

And this is how it's done: Rosetta emits radio waves, which penetrate the comet nucleus and reach Philae on the other side of the nucleus. Philae immediately returns the radio waves with its aerial.

What is the aim of this radio wave ping-pong? As it travels through the celestial body, the signal changes and thus enables conclusions to be drawn about the interior.

"The inner structure of a comet is still largely unknown," explains Böhnhardt. "We want to know for example whether it is more a loose accumulation of snow or mainly solid components."

An important aspect is whether there are larger voids or layers on the nucleus. "Better data on the structure of the comet will help us to understand the exact formation process of the large bodies in the solar system, the planets," explains Hermann Böhnhardt.

These accrete from smaller bodies in a multi-stage process according to the topical theories.