What samples from space have taught us

Alastair Gunn explains what scientists have learnt in the 20 years since the first unmanned mission brought materials back from alien worlds

- 

One of the best ways to study the Universe is to inspect actual materials from our celestial neighbours.

Some naturally fall to Earth as meteorites, but these are few and far between, limited in their origins and are not likely to be pristine. That's why scientists have put great efforts into remotely grabbing samples of the Solar System's worlds and returning them to Earth. These sample-return missions (SRMs) provide important insights which cannot be obtained by any other means.

Scientists use a huge range of exotic-sounding techniques to analyse these samples, including electron microscopy, spectroscopic analysis, isotope analysis and even muon beam imaging. Together, the results can reveal a treasure trove of data: when, where and how the object formed, its history and evolution, and its relation to other objects.

So far, there have been 17 successful SRMs which all told have returned about 384kg (847lb) of Moon rocks, about 128g (4.5oz) of asteroid material and about one milligram (0.000035oz) of comet dust to Earth. So, what have these missions taught us about the Solar System?

Lunar rock

Lunar samples were first returned by the six manned Apollo missions, the Soviet Union's three robotic Luna missions and, most recently, China's Chang'e 5 and 6.