So far, Earth is the only place in the universe that we know for sure is home to life, but there's evidence that its chemical building blocks may start stacking up in space. Now, NASA astrophysicists have managed to create DNA sugars in a vacuum chamber that simulates interstellar space, and in follow-up studies found other sugar derivatives in meteorite samples.
Exactly how life got started on Earth remains a mystery, particularly the leap from non-living matter to living cells. The current leading theory is that surface hot springs or deep-sea hydrothermal vents provided the right conditions and ingredients to give birth to simple life, but there are still some plot holes to be patched up.
An emerging alternative is that Earth was merely the "oven" for the cake of life – the batter may have been mixed in space. It may sound far-fetched, but the evidence for this is growing. Light signatures of sugars and molecules with the right structure and geometry for life have been detected out in space, while water and compounds essential for life have been found in meteorites.
The new study adds to that evidence. Scientists from NASA's Ames Research Center set out to see whether DNA sugars could be created in interstellar space. To do so, they cooled an aluminum substance almost to absolute zero, and placed it in a vacuum chamber that recreated the conditions of deep space. Then, the team added a gas mixture of water vapor and methanol – components of the interstellar medium – and finally they beamed UV light into the chamber to mimic radiation from stars.
Thanks to the extremely cold temperature, an icy layer was found to form on the aluminum, which was then warmed up by the UV radiation. The team then analyzed the substance and found that the sugar molecule 2-deoxyribose – which puts the D in DNA – had been created, along with several other sugar derivatives.
But just because these vital molecules can be created in the lab while simulating a deep space environment, doesn't necessarily mean that the process does happen in nature. To investigate, the team examined several carbonaceous meteorite samples and found traces of more simple deoxysugar acids and alcohols. Nothing as complex as 2-deoxyribose was found, but the team says this could be because they haven't checked many samples yet.
"For more than two decades we've asked ourselves if the chemistry we find in space can make the kinds of compounds essential to life," says Scott Sandford, an author of the study. "So far, we haven't picked a single broad set of molecules that can't be produced. The universe is an organic chemist. It has big beakers and lots of time — and the result is a lot of organic material, some of which is useful to life."
Finding these vital molecules in meteorites could help explain the origin of life on Earth, as well as ramping up the likelihood of it being widespread throughout the universe. Asteroids and comets could be exposed to this cosmic dust, going on to seed planets and moons with life as they crash to the surface.
"We don't yet know whether life is common in the universe, but we're pretty sure the presence of life's building blocks is not a limiting factor," says Michel Nuevo, lead author of the study.
The research was published in the journal Nature Communications.
Source: NASA Ames Research Center