They're finding out that those swings may be wider than first thought.
The rover is sampling ground and air temperatures as it meanders around the Martian surface and over the course of one day NASA found that the temperature extremes were substantially larger than 100 degrees.
|Graph courtesy NASA and JPL-Caltech|
If you think Millville and the Pinelands can get cold at night...they've got nothing on Mars. Oh, and the "humidity" in Mars makes the Sahara look like a tropical paradise in comparison.
You can check out the temperature readings on Mars whenever you want during the course of the mission.