Relevance of Samples From Solar System Bodies
Humanity was until now able to collect samples of six identified Solar System bodies as well as samples of the solar wind. These samples were acquired through three methods: The collection of samples of Earth itself, the collection of meteoroids that have fallen on Earth, and the collection of samples through sample return missions. Samples of Moon rock from Earth's Moon were collected both from meteorites and through unmanned and manned sample return missions. The comet Wild 2 and the asteroid 25143 Itokawa were visited by unmanned spacecraft which returned samples to Earth. Furthermore samples for three identified Solar System bodies were only collected by means other than sample return missions: These are samples from Earth itself, samples from Vesta in the form of HED meteorites and and samples from Mars in the form of Martian meteorites.
Such samples available on Earth can then be analyzed in laboratories and enable us to further our understanding and knowledge as part of the discovery and exploration of the Solar System. Until now many important scientific discoveries about the Solar System were made remotely with telescopes, and some Solar System bodies were visited by orbiting or even landing spacecraft with instruments capable of some forms of remote sensing or even sample analysis. While such an investigation of our Solar System is technically easier than a sample return mission, the scientific tools available here on Earth to study such samples are far more advanced and diverse than what can currently be carried by spacecraft. Analysis of samples on Earth allows to follow up any findings with different tools, or even allows to use tools in the future that have yet to be developed – in contrast a spacecraft can carry only a limited set of analytic tools and these have to be chosen and build long before the spacecraft reaches its target.
The results of such sample analysis on Earth makes it then possible to match findings made be remote sensing and enables us to gain more insight into the processes that formed the Solar System. This was done for example with findings by the Dawn spacecraft which visited the asteroid Vesta from 2011 to 2012 for imaging, and samples from HED meteorites (collected on Earth until then) which were compared to data gathered by Dawn. These meteorites could then be identified as material ejected from the large impact crater Rheasilvia on Vesta. It was then through this that the composition of crust, mantle and core of Vesta was deducted. Similarly some differences in composition of asteroids (and to a lesser extent different compositions of comets) can be discerned by imaging alone. However to get a more precise inventory of the material present on these different bodies more samples will be collected in the future, to match the compositions of the samples returned by spacecraft with the data gathered through telescopes.
One further focus of such investigation – besides the basic composition and geologic history of the various Solar System bodies – is the presence of the building blocks of life on comets, asteroids, Mars or the moons of the gas giants. Several sample return missions to asteroids and comets are currently in the works. More samples from asteroids and comets will help answer the question if some of the building blocks of life formed in space and were carried to Earth in the form of meteorites. Another question under investigation is whether extraterrestrial life formed on other Solar System bodies like Mars or on the moons of the gas giants, and if life might even exist there today. The result of NASA's last "Decadal Survey" was to prioritize a Mars sample return mission, as Mars has a special importance: it is comparatively "nearby", might have harbored life in the past, and might even be able to sustain life today. Jupiter's moon Europa is another important focus in the search for life in our Solar System. However due to the distance and other constrains Europa might not be the target of a sample return mission in the foreseeable future.
Read more about this topic: Sample Return Mission
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