The Study of Extraterrestrial Matter The study of extraterrestrial matter plays a central role in the current search for life. It mostly concerns the possible detection of organic compounds, or the presence of water. However, a major problem is that our direct access to matter that did not originate on the Earth is extremely limited. In fact, the only possibilities we have to analyse extraterrestrial matter are the meteorites that happen to fall on the Earth and are picked up on the surface, some cosmic dust particles (mostly from comets and asteroids, but some are from interstellar space) that are collected high in the Earth's atmosphere, or the in-situ (e.g., on the spot) analysis by means of space missions to other celestial bodies. In addition, the Apollo astronauts carried several hundred kilograms of lunar dust and rock back to the Earth that, like the meteorites and cosmic dust grains, have been extensively analysed in terrestrial laboratories - some additional material was returned by the Luna spacecraft. These laboratories have the best possible equipment and allow an extremely detailed study of the properties of the material. In the future, it may also become possible to bring back to the Earth samples of matter from other Solar System objects. Until now, such studies had to rely on less complex instruments on the spacecraft and could therefore not be so detailed and accurate.

Giotto approaching Comet Halley A cosmic grain particle, captured in the stratosphere (NASA)