Kneeling on the edge of a deep crater, astronaut Alexander Gerst uses a chisel to collect a sample of volcanic rock which he carefully puts inside a white plastic bag.

Gerst is not on the Moon, even if it looks like it. He is in the middle of Los Volcanes Natural Park on the island of Lanzarote in Spain's Canary Islands, off the northwest coast of Africa.

With its blackened lava fields, craters and volcanic tubes, Lanzarote's geology can be uncannily similar to that of the Moon and Mars—so much so that the European Space Agency (ESA) and NASA have for years been sending astronauts to the island to train.

"This place has lavas that are very, very similar to the ones that we find on the Moon," Gerst, a 46-year-old German astronaut with the ESA, told AFP.

He said the island was "a unique training ground".