Scientists find all building blocks necessary for DNA in meteorite

By: April Carson



The finding adds to previous findings that show life's beginnings originated from space.


In April, researchers found that space rocks that slammed to the planet in recent centuries retain the five bases needed to store information in DNA and RNA. Caught in the Earth's gravitational pull, they then fall to the planet as meteorites.


All life on Earth is made up of these "nucleobases" - adenine, guanine, cytosine, thymine, and uracil - which are combined with sugars and phosphates to form the genetic code. Whether these fundamental chemicals for life originated from space or formed in a warm pool of terrestrial chemistry is still unknown (SN: 9/24/20). However, this finding supports the idea that pre-life molecules were imported from space.


Since the 1960s, scientists have discovered organic compounds such as adenine, guanine, and other in meteorites (SN: 8/10/11, SN: 12/4/20). Uracil has also been detected but cytosine and thymine were still eluding researchers until now.


“We've finished the set of all the bases discovered in DNA and RNA, as well as life on Earth, and they're present in meteorites," says astrochemist Daniel Glavin of NASA's Goddard Space Flight Center in Greenbelt, Maryland.


The new discovery also has implications for the origin of life on Earth. The most common theory is that Life could have started on Earth after meteorites delivered the necessary building blocks (SN: 4/15/19).


Yasuhiro Oba of Hokkaido University in Sapporo, Japan, and colleagues developed a method to gently extract and separate different chemical compounds from liquefied meteorite dust and then analyze them several years ago.


“Our detection method has orders of magnitude greater sensitivity than those previously used in the field,” Oba says. In 2011, researchers employed this same approach to find ribose, a sugar necessary for life, in three meteorites (SN: 11/22/19).



Oba and colleagues teamed up with NASA astrochemists in a new study to analyze one of the three Martian meteorite samples and three more, looking for another kind of essential chemical for life: nucleobases.


The researchers believe that their milder extraction process, which employs cold water rather than acid, preserves the chemicals. “We're seeing that this extraction technique works really well for these delicate nucleobases,” Glavin adds. It's more like making a cold brew than hot tea, according to Glavin.


The researchers looked for amino acids, bases and other compounds linked to life in four meteorites that fell decades ago in Australia, Kentucky, and British Columbia using this approach. The team detected adenine, guanine, cytosine, uracil, thymine, several base-related compounds as well as a few amino acids in all four samples.


Scientists have long believed that meteorites contain the building blocks necessary for DNA, and a new study confirms this hypothesis. Researchers used a novel extraction technique to identify all of the key chemicals in four different meteorites, including adenine, guanine, cytosine, uracil, thymine, and several base-related compounds. The team also detected several amino acids, including alanine, glycine, and aspartic acid.


The team also used this approach to measure chemical abundances in soil from the Australia site and compare them with the measured meteorite values. For several identified chemicals, the meteorite values were greater than those in the surrounding soil, implying that they arrived on Earth in these rocks.


The soil abundances of other discovered components, such as cytosine and uracil, are 20 times higher than in the meteorites. This might indicate earthly contamination, according to cosmochemist Michael Callahan of Boise State University in Idaho.


“They seem to have correctly identified these chemicals,” Callahan adds. “However, they didn't provide enough compelling data to convince me that they were truly extraterrestrial.” Callahan previously worked at NASA and collaborated with Glavin and others on studies of organic materials in meteorites.


According to Glavin and his coworkers, there are a few specific identified chemicals in the extraterrestrial mix that lend support to the idea of an interplanetary origin. The researchers discovered more than a dozen additional life-related compounds, including isomers of the nucleobases, in the new study, according to Glavin. Isomers have identical chemical formulas to their corresponding bases but have different component arrangements. Some of those isomers were found in the meteorites but not in the soil. "If there had been soil contamination, we would have seen those isomers in the soil as well," he adds.


Removing the lead from the equation by going straight to the source of such meteorites — pristine asteroids — might be a solution. Oba and coworkers are already extracting samples from Ryugu's surface with their method, which will be used on OSIRIS-REx mission samples when they reach Earth in late 2020 (SN: 12/7/20). In September 2023, NASA's OSIRIS-REx spacecraft is scheduled to return with similar materials from Bennu (SN: 1/15/19).


“The material is helping us tell new stories,” Glavin adds. “It’s exciting to find new building blocks for DNA that we can use in the lab, and it’s even more exciting to think about what these findings might tell us about other potentially habitable worlds.”








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About the Blogger:


April Carson is the daughter of Billy Carson. She received her bachelor's degree in Social Sciences from Jacksonville University, where she was also on the Women's Basketball team. She now has a successful clothing company that specializes in organic baby clothes and other items. Take a look at their most popular fall fashions on bossbabymav.com


To read more of April's blogs, check out her website! She publishes new blogs on a daily basis, including the most helpful mommy advice and baby care tips! Follow on IG @bossbabymav


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