Planetary scientist Wim van Westrenen wants to understand how the Moon evolved through time to become what it is today. He subjects rock samples to high pressures and temperatures – or nowadays gets his team members to do that for him – and tries to deduce the properties of the interior of the Moon from his results.
Imagine you have bought a birthday cake and you want to deduce how it was made. How many eggs did the pastry chef use, how much butter or margarine? How long did he bake it, and what temperature did he set the oven to? That is what petrologist (rock scientist) Wim van Westrenen (born 1973) and his colleagues at VU University Amsterdam’s Faculty of Earth and Life Sciences try to do. The only difference is that they are not interested in cakes (not professionally, at any rate), but in the Moon. And they don’t use an oven, but a high-pressure device weighing one and a half tons. They place small samples of finely powdered rock into the press and subject them to temperatures of more than 1500 °C and pressures in excess of 30,000 atmospheres, to mimic the conditions prevailing many kilometres beneath the surface of the Earth or the Moon. “Our question is: what mineral mix do I have to melt at what temperature and pressure to make lava that is identical with surface samples found at specific locations? When I know what the conditions were when that lava sample was formed, I know that those conditions must have prevailed in the interior of the Earth or the Moon during their formation.” Van Westrenen and his colleagues use a variety of cunning tricks like this to figure out how the Moon changed with time.