Nature: Two proponents of the theory that life originated at deep-sea thermal vents have published a paper explaining how cellular ion pumps could have evolved. In present-day cells, the energy released by the flow of ions across the cell membrane is used to create the cells’ principal source of fuel, ATP. The ion transfer is mediated by proteins, whose production by cells is fueled by ATP. A paradox therefore arises: Which came first, ion pumps or cells? Nick Lane of University College London and Bill Martin of the University of Düsseldorf in Germany argue that an ion gradient could be produced by the combination of alkaline and acidic water in the iron- and sulfur-rich rocks of thermal vents. Small pores in the rocks would serve as the cell membrane, allowing for the passing of ions but trapping larger atoms and molecules. That would concentrate any simple organic molecules that formed and enable the creation of complex proteins and RNA molecules. Over time, an organic membrane, which mimicked the ion gradient of the rock, could have formed as well, and when it fully surrounded the proteins and RNA, it could have formed the first true cells.
Daily Archives: December 21, 2012
California meteorite provides wealth of information
Science News: Almost 1 kg of fragments have been collected from a carbonaceous chondrite meteorite that fell in California in April 2012. Carbonaceous chondrites are carbon-rich and make up only 3% of known meteorites. The California find, known as the Sutter’s Mill meteorite, belongs to a subgroup particularly rich in organic molecules. Researchers from the University of California, Davis, found more than 70 different chemical elements in the meteorite and were able to date it to the formation of the solar system. However, the mix of compounds suggests that it was part of an asteroid formed by the aggregation of a large number of smaller asteroids. Based on the effect of cosmic rays on the material, researchers have deduced that the meteorite was broken off of the asteroid approximately 50 000 years ago. It also appears to have followed an unusual path before striking Earth. Peter Jenniskens, from the SETI Institute in California, says that the meteorite likely came from a family of asteroids in the belt between Mars and Jupiter. The wear markings on it suggest that the asteroids have experienced more collisions than expected. And the way it reflects light is similar to the asteroid that will be visited by Japan’s Hayabusa-2 spacecraft in 2018.