Look for the Improbable in Extraterrestrial Life

To land a spacecraft on Europa, with the heavy equipment needed to penetrate the ice and explore the ocean directly, would be a formidable undertaking. A direct search for life in Europa's ocean would today be prohibitively expensive. But just as asteroid and comet impacts on Mars have given us an easier way to look for evidence of life on that planet, impacts on Europa give us an easier way to look for evidence of life there. Every time a major impact occurs on Europa, a vast quantity of wat...

 Mammals Produce Useless Yolks

Vestigial genes can go hand in hand with vestigial structures. We mammals evolved from reptilian ancestors that laid eggs. With the exceptions of the “monotremes” (the order of mammals that includes the Australian spiny anteater and duck-billed platypus), mammals have dispensed with egg-laying, and mothers nourish their young directly through the placenta instead of by providing a storehouse of yolk. And mammals carry three genes that, in reptiles and birds, produce the nutritious protein...