NASA researcher Jen Heldmann installs sensors at Pearse Valley in the McMurdo Dry Valleys to study what happens to ice in the subsurface. The pile of rocks shown in the foreground protects the data logger which records data year-round. The sensors include multiple temperature and humidity probes, which provide information on whether the subsurface snow at this location is stable, whether it melts, or whether it sublimes. Buried snow may be an analogue to the buried snow-like material that the Phoenix lander saw on Mars. Heldmann and Chris McKay are co-principal NASA investigators.