![]() “And it became very clear to me that we were both converging on the fact that there was a missing ‘driving force’ before biology.” “Sara and I were discussing information theory and life and minimal routes to build self-replicating machines,” Cronin recalled. Something, Walker mused, must have guided that process even before Darwinian selection took over.Ĭronin and Walker joined forces after attending a NASA astrobiology workshop in 2012. Walker, meanwhile, had been wrestling with the question of life’s origin - an issue closely related to making complex molecules, because those in living organisms are far too complex to have been assembled by chance. “Assembly theory was developed to capture my intuition that complex molecules can’t just emerge into existence because the combinatorial space is too vast,” Cronin said. It’s one thing to say that an object is possible according to the laws of physics it’s another to say there’s an actual pathway for making it from its component parts. Paul Davies, a physicist at Arizona State agrees, calling it “a novel idea with the potential to transform the way we think about complexity.” On the Order of ThingsĪssembly theory started when Cronin asked why, given the astronomical number of ways to combine different atoms, nature makes some molecules and not others. Assembly theory, he said, offers a way to discover the contingent histories of objects - an issue ignored by most theories of complexity, which tend to focus on the way things are but not how they got to be that way. “It’s fun to engage with,” said the evolutionary theorist David Krakauer, president of the Santa Fe Institute. And some scientists wonder whether assembly theory can even deliver on its more modest promises to distinguish life from nonlife, and to think about complexity in a new way.īut others feel that these are still early days for assembly theory, and there’s a real chance that it might bring a fresh perspective to the question of how complexity arises and evolves. Its proponents have not yet made clear how it might be tested in the lab. Not surprisingly, such an ambitious project has aroused skepticism. It even seeks to answer a question that has perplexed scientists and philosophers for millennia: What is life, anyway? And it seeks that explanation not, in the usual manner of physics, in timeless physical laws, but in a process that imbues objects with histories and memories of what came before them. As laid out in a recent series of publications, it attempts to explain why apparently unlikely things, such as you and me, even exist at all. Their method, they said, simply assumes that alien life forms will produce molecules with a chemical complexity similar to that of life on Earth.Ĭalled assembly theory, the idea underpinning the pair’s strategy has even grander aims. In 2021, a team led by Lee Cronin of the University of Glasgow in Scotland and Sara Walker of Arizona State University proposed a very general way to identify molecules made by living systems - even those using unfamiliar chemistries. These and other missions on the horizon will face the same obstacle that has plagued scientists since they first attempted to search for signs of Martian biology with the Viking landers in the 1970s: There is no definitive signature of life. And in 2027, NASA plans to launch a dronelike helicopter called Dragonfly to buzz over the surface of Saturn’s moon Titan, a hazy, carbon-rich world with liquid hydrocarbon lakes that might be just right for hosting life - but not as we know it. Both spacecraft have onboard instruments that will look for the fingerprints of complex organic molecules - a possible hint of life beneath the ice. Next year, NASA’s Europa Clipper spacecraft will launch, also aiming for Europa. One of those moons, Europa, has a deep, briny ocean beneath its frozen crust and is among the most promising places in the solar system to look for alien life. In April, the European Space Agency’s Juice spacecraft blasted off from French Guiana on a course to Jupiter and its moons. Scientists might even spot the signatures of such life forms without knowing they’re the work of biology. There’s no guarantee that alien biology would use the same chemistries as on Earth, with familiar building blocks such as DNA and proteins. Life on other worlds - if it exists - might be so alien as to be unrecognizable. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |