Question: Rain, You Have a photo on your profile of a diagram? Explain it?

Rain Irshad answered on 19 Mar 2012:

This is a rig for calibrating seismometers. When you calibrate something, you put a scale on it, like the one on thermometers so you know exactly what height goes with which temperature.

We do this by using something that already has a scale and then cross-checking the new instrument with the known one. On top of the big granite block is a seismometer that you can buy for earthquake research on Earth. This is the kind they bury underground to predict earthquakes, measure tremors, stuff like that. That has to stay at Earth temperature to work properly.

Underneath the block, we’ve got tiny seismometers for Mars. When you smack the granite, both seismometers measure a wobble and you can put a scale on the tiny ones. The Martian ones need to be tested under Martian conditions, though, so we surround it with Copper and pour liquid nitrogen through it. The copper gets really cold and so does the seismometer.

But the air on Mars is different too, so we put a vacuum chamber around the whole lot and suck all the air out. Then we can add stuff that might be on Mars – lots of carbon dioxide, for example.

The whole thing is rested on top of a frame with springy bits in the legs. That makes sure that any vibrations from the ground are absorbed and don’t get carried to the seismometer. Otherwise, it’ll just be measuring the people walking up and down the lab.