
The Spirit and Opportunity rovers brought something brand new to space exploration: cuteness. The rovers' solar panels vaguely resemble wings, the camera masts look like long necks, and the Pancam instruments – two on the top of each rover's mast – seem to be the "eyes" of space-faring creatures. I'm certainly not the first to say this; in a press conference, Callas even called them "the cutest darn things out in the solar system."
Why is cuteness so important? Because humans tend to respond emotionally to cute things. We can't help it. It's hardwired into us, as it's related to our instincts to protect our young. OK, you say, but Spirit doesn't look at all like a human baby. To that I would reply: in ways that matter, it actually does.
It's not necessarily "human" characteristics that trigger this biological response in us; rather, it's the "juvenile" characteristics. Things that are cute tend to exhibit the characteristics that distinguish juvenile humans from adults, such as big eyes, flat faces, and large foreheads. These are the characteristics that make us go "awww" when we see puppies and that compel us to watch videos of kittens on YouTube.
In a fascinating article (PDF) written for Natural History magazine, paleontologist and evolutionary biologist Stephen Jay Gould wrote, "When we see a living creature with babyish features, we feel an automatic surge of disarming tenderness. The adaptive value of this response can scarcely be questioned, for we must nurture our babies." He argues that "abstract features of human childhood elicit powerful emotional responses in us, even when they occur in other animals,"[. . .]
Gould also showed that we can quantify cuteness. In that same 1978 Natural History article, titled "A Biological Homage to Mickey Mouse,"he measured three characteristics of Mickey's face to show that everyone's favorite mouse had grown cuter over 50 years: (1) eye size as a percentage of head length (base of the nose to the top of rear ear); (2) head length as a percentage of body length; and (3) cranial vault size measured by rearward displacement of the front ear (base of the nose to top of front ear as a percentage of base of the nose to top of rear ear).
Rice concludes that Spirit--and Opportunity--are as cute as Mickey Mouse.