1 Martian 1: Right, I've had enough of this. I'm gonna teach that stinkin' Mars Rover a lesson.
2 Martian 2: Be careful. It's semi-autonomous.
2 Martian 1: Oh, what's it gonna do? Run over me at 0.18 km/h?
3 {Scene change: Martian plateau}
3 Martian 1: {getting seriously drilled as he attempts to beat the Rover with a wrench} Ow! Ow! Hey! Stop it! Ow!
4 {Scene change: Earth}
4 NASA Guy 1: Hmmm. According to the latest Mössbauer spectrum, the rock abrasion tool has hit something really soft...

Scientific accuracy: The top speed of the rovers Spirit and Opportunity is indeed 0.18 kilometres per hour.

Artistic licence: A Mössbauer spectrum does not reveal the hardness of an object. It reveals the chemical environment of particular targeted atomic nuclei in a sample by measurng the relative absorption of gamma rays that are Doppler shifted by different amounts. For example, Opportunity's measuremnent of the Mössbauer spectrum of the soil at Meridiani Planum revealed the existence of the iron-bearing mineral olivine.

"Mössbauer" is, however, a cool-sounding word, so I can use it if I want to. I just want you to know what it really means. What other webcomic teaches you more physics?

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2013-01-25 Rerun commentary: The problem with the Martian LEGO minifigures is that their hands don't rotate like human figs. Thus the awkward angle at which he's holding the spanner.

The background image in panel 3 is an actual image of Meridiani on Mars as taken by Opportunity.