Scientists can imitate what happened in the distant past. In the new tests, they beamed a high-energy laser onto a simple chemical. Called formamide, it probably was common on Earth long before life began. Scientists beamed the laser energy onto formamide in hopes of simulating the energy that would be released when an asteroid collided with Earth.
In these new tests, the laser’s energy proved strong enough to form genetic fragments. They are called nucleobases (often simply called bases.) All living things contain two types of genetic molecules. One, called DNA, is shaped like a twisted ladder. Pairs of nucleobases form its rungs. The other type of genetic molecule, called RNA, also uses pairs of these bases, but they form different structures.
“We were looking for the simplest possible scenario in which these nucleobases could have formed,” David Nesvorný told Science News. He’s a planetary scientist at the Southwest Research Institute in Boulder, Colo.
Why did Nesvorný and his coworkers work with formamide? The smelly liquid contains nitrogen and was likely around on early Earth. Other studies had shown that the chemical can break apart and form bases. But those studies had used other chemicals to break down the formamide. Nesvorný’s group used a laser’s energy instead. They wanted to create the conditions of an asteroid collision in the lab.
“These impacts of the past had enormous energy,” Nesvorný explains. Imagine, for example, a rock the size of Rhode Island smashing into Earth at more than 30 times the speed of sound. The energy of such an impact would cause some unusual chemical reactions, he points out.
Four billion years ago, such collisions were not unusual. During a period scientists call the Late Heavy Bombardment, space rocks rained down on Earth. To re-create the energy of those impacts, the scientists beamed light from a high-powered laser at a small pool of formamide. In the goo that was left, they found new molecules: RNA and DNA bases.