Curiosity cleanup
In the article “Protecting the planet” (SN: 11/3/12, p. 32), the sidebar “Keeping Mars clean” gives the impression that Curiosity had not been contaminated, while the opposite is true. Apparently the sterilized craft was opened up and microbial contamination likely occurred. Curiosity’s drill bits may be contaminated with Earth microbes. So now NASA is in the catch-22 position that if they do find water they cannot use the drill. The entire gist of the article is to give an erroneous impression that Curiosity was clean, when in fact Catharine Conley has been quoted saying that she knew Curiosity was contaminated.
Dennis Kuzara, Punta Gorda, Fla.

A box of sterilized drill bits meant for use on Mars was opened on Earth so one could be installed on the rover. While this handling was less than optimal, Conley says, after several reviews the Mars Science Laboratory (Curiosity) mission is still in compliance with NASA and international policy. As for the article in Science News, “The statement is true that MSL is the cleanest spacecraft sent to Mars since the Viking [missions],” Conley says. Curiosity carries about the same total number of spores, but fewer spores per square centimeter, than the much smaller spacecraft that included the rovers Spirit, Opportunity and Pathfinder. The Viking landing craft initially had more spores than Curiosity, but prelaunch baking knocked down the number of viable spores to less than the number carried by Curiosity. —Tina Hesman Saey

Face effects
The Thatcher effect described in “Face Smarts” (SN: 10/6/12, p. 20), in which altered upside-down faces appear normal, fails in my household. My wife, an artist, spotted all the facial anomalies immediately, apparently because she is acutely aware of such details by her training and abilities. I, an amateur artist, spotted the anomalous eyes immediately but not the lips. Perhaps a larger picture with more detail would have had me equal my wife’s performance.
Irwin Tyler, Spring Valley, N.Y.

Earthlike bias
Planetary Peekaboo” (SN: 9/22/12, p. 26) appears to make a very common assumption: All life must be like Earth life. That is, it requires liquid water, among other things. But this is really Earth-chauvinism. Just because all life we know about requires liquid water doesn’t mean that there can’t be life that doesn’t. When looking for life elsewhere in the universe, we shouldn’t limit ourselves to Earthlike planets. We should keep an open mind.
Ted Grinthal, Berkeley Heights, N.J.

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