Life molecules 'sniffed' by Philae
Organic molecules, which include the raw materials for life, have been "sniffed" by the Philae comet probe, scientists have confirmed.
The chemicals, possibly kicked up in dust, were floating around the probe after it landed on comet 67p/Churyumov-Gerasimenko a week ago.
However, first reports from an analysis of samples drilled from the comet surface by Philae have been disappointing.
The drill apparently delivered something to one of the lander's ovens, where samples are supposed to be heated and vaporised for analysis. But although the oven heated up, the data showed nothing.
Scientists are checking to see if there is a problem with the drill or the German-built Cosac (Cometary Sampling and Composition Experiment) instrument that was studying the samples.
The fact that Cosac detected organic molecules is not in itself a surprise and in no way suggests that the comet harbours "seeds of life".
Comets have long been known to be rich in organic molecules, which are simply molecules containing carbon. Methane is a basic organic molecule.
But more complex organic molecules, such as amino acids, provide the building blocks for carbon-based life and many scientist believe comets may have brought them to Earth.
If amino acids are found on comet 67P scientists will be keen to discover their "chirality", or handedness - the way their structure adopts one of two mirror images. That is because life on Earth only uses left-handed versions of amino acids in its proteins.
Philae has also shown that beneath a surface layer of dust the comet is much harder than expected.
An instrument called Mupus (Multi-Purpose Sensors for Surface and Sub-Surface Science) extended on the end of a five-foot arm hammered a probe into the comet surface but was unable to penetrate very far.
Scientists believe it came up against a layer of hard ice.
Professor Tilman Spohn, from the German space agency DLR's Institute of Planetary Research, said: "Although the power of the hammer was gradually increased, we were not able to go deep into the surface.
"Using comparative measurements performed in the laboratory, we estimate that the probe must have likely encountered a layer with the same strength as ice under a 10 to 20-centimetre thick layer of dust."
Philae was carried to the comet by the Rosetta orbiter, which took 10 years to complete its epic four billion-mile journey across space.
The probe made a dramatic landing, bouncing twice before coming to rest in the shadow of a crater wall more than half a mile from its original landing site on the comet, which is more than 300 million miles from Earth.
Scientists tried to reposition the lander to expose more of its solar cells to sunlight, but had to put the probe to sleep as its battery power died.
It is hoped that as comet 67P flies closer to the Sun enough light will become available to re-activate Philae.
DLR's scientific director for the lander, Dr Ekkehard Kuhrt, said: "We have collected a great deal of valuable data, which could only have been acquired through direct contact with the comet. Together with the measurements performed by the Rosetta orbiter, we are well on our way to achieving a greater understanding of comets. Their surface properties appear to be quite different than was previously thought."
A decision not to engage a British instrument, Ptolemy, to analyse drill samples was taken because it uses up too much power.