Interstellar clouds may have helped with life on Earth

12 Jan. () –

Interstellar cloud conditions may have played an important role in the presence of basic components of life in the solar system.

This is what a new study led by Dr. Danna Qasim, a researcher at the Southwest Research Institute (SwRI).

“Carbonaceous chondrites, some of the oldest objects in the universe, are meteorites believed to have contributed to the origins of life. They contain several different organic molecules and substances, including amines and amino acids, which are key building blocks of life which were essential to create life on Earth. These substances are needed to create proteins and muscle tissue,” Qasim explained. it’s a statement.

Most meteorites are fragments of asteroids that broke up long ago in the asteroid belt, located between Mars and Jupiter. These fragments orbit the Sun – sometimes for millions of years – before colliding with Earth.

One of the questions that Qasim and other researchers are trying to answer is how the amino acids got into the carbonaceous chondrites. Since most meteorites come from asteroids, scientists have tried to reproduce amino acids by simulating asteroid conditions in a laboratory, a process called “aqueous alteration”.

“That method hasn’t been 100% successful,” Qasim says. “However, the composition of the asteroids originated from the parent interstellar molecular cloud, which was rich in organics. Although there is no direct evidence for amino acids in interstellar clouds, there is for amines. The molecular cloud could have provided amino acids to asteroids, which passed them on to meteorites.”

To determine the extent to which amino acids formed from asteroid conditions and the extent to which they were inherited from the interstellar molecular cloud, Qasim simulated the formation of amines and amino acids just as it would occur in the interstellar molecular cloud.

“I created ices that are very common in the cloud and irradiated them to simulate the impact of cosmic rays,” explained Qasim, who conducted the experiment while working at NASA’s Goddard Center between 2020 and 2022. “This caused the molecules to break apart and recombine into larger molecules, ultimately creating organic residue.”

Qasim then reprocessed the residue by recreating asteroid conditions through aqueous alteration and studied the substance, looking for amines and amino acids.

“Regardless of the type of asteroid processing we did, the amine and amino acid diversity of the interstellar ice experiments remained constant,” he said. “That tells us that interstellar cloud conditions are quite resistant to asteroid processing. These conditions could have influenced the distribution of amino acids that we found in meteorites.”

However, individual amino acid abundances doubled, suggesting that asteroid processing influences the amount of amino acids present.

“Essentially, we have to consider both the interstellar cloud conditions and the processing by the asteroid to better interpret the distribution,” he said.

Qasim looks forward to studies of asteroid samples from missions such as OSIRIS-REx, which is currently en route to Earth to deliver samples from asteroid Bennu here in September, and Hayabusa2, which recently returned from asteroid Ryugu, to better understand the role that the interstellar cloud played in the distribution of the building blocks of life.

“When scientists study these samples, they usually try to understand what the asteroid processes influence, but it is clear that now we need to study how the interstellar cloud also influences the distribution of the building blocks of life,” explains Qasim.

The work is published in the journal ACS Earth and Space Chemistry.