Detailed investigation of samples from the asteroid Ryugu has provided further evidence that the organic molecules that gave rise to life on our planet were brought here by ancient comets.
These space rock samples were Returned to Earth by the Japanese Hayabusa2 missionwhich visited the top-shaped Ryugu space rock in 2018. Hayabusa2 spent around 18 months studying the asteroid and collecting material from the surface, which has proven to be a treasure trove of information about our Solar system.
Ryugu, formally known as 162173 Ryugu, is a 2,850-foot (870-meter) wide near-Earth asteroid that lacks a protective atmosphere. This means that its surface is directly exposed to space and can accumulate interplanetary dust, which changes the composition of the asteroid’s surface when it is impacted.
The team of scientists behind new developments in the search for the origins of life found “fusion splashes” 5 to 20 micrometers wide created when particular cometary dust was thrown onto Ryugu’s surface. And within these melted splatters, the researchers found tiny carbonaceous materials similar to primitive organic matter.
“This organic matter could be the tiny seeds of life that were once delivered from space to Earth,” said team member Megumi Matsumoto, an assistant professor at Tohoku University’s Graduate School of Science. said in a statement.
Comets tend to exist in wide orbits around the sun, meaning they spend most of their time in the icy outer edges of the solar system. But when they enter the inner solar system, solar radiation heats their icy interior material. This causes the material to transform directly into gas, a process called sublimation.
As this gaseous material explodes from the comet, it carries with it some of the object’s surface material. This not only creates the tails and auras or “comas” characteristic of comets, but also leaves trails of cometary dust around the sun. When Earth passes through these paths, we witness meteor shows as dust fragments burn up in our planet’s atmosphere.
This cometary material is much more likely to reach the surface of bodies without an atmosphere like Ryugu, where it can nevertheless be preserved. Therefore, studying those dust remnants in the Hayabusa2 samples could reveal clues about the material in the early solar system.
The fusion splashes studied by the team were created when material on the asteroid’s surface was struck by cometary dust, and the two materials melted and mixed during the heating caused by the impact and eventually cooled.
The spongy carbonaceous materials found in Ryugu melts differ chemically from the organic matter normally found in cometary material because they lack oxygen and nitrogen. However, this could give insight into how the material was formed in the first place.
“We propose that the carbonaceous materials formed from cometary organic matter through the evaporation of volatiles, such as nitrogen and oxygen, during impact-induced heating,” Matsumoto said. “This suggests that cometary matter was transported to the near-Earth region from the outer solar system.”
Sealed with the melts as additional evidence of its origin, there are small voids caused when impacts released water vapor from materials on Ryugu’s surface; This water was captured by matter heated by the impact.
“Our 3D CT images and chemical analyzes showed that the molten splashes mainly consist of silicate glasses with voids and small inclusions of spherical iron sulfides,” Matsumoto added. “The chemical compositions of the melt splashes suggest that Ryugu’s hydrated silicates were mixed with cometary dust.”
Matsumoto and the team continue to examine Ryugu samples collected by Hayabusa2 in hopes of discovering more melts that may contain evidence of cometary dust impacts.
The hope is that this will provide more information about the transport of primordial organic material into space around Earth more than 4 billion years ago, before the emergence of life.
The team’s research is published in the journal. Scientific advances.
Originally published in space.com.