Did Hitchhiking Sugars on Asteroids Help Jumpstart Life on Earth?

Scientists found sugars while analyzing meteorites, adding to a popular theory about how life began on Earth.

NASA/Goddard/University of Arizona
  • Collaborators from Japan and NASA have found several kinds of sugars on two meteorites.
  • Scientists continue to theorize about the conditions that fostered the birth of life on Earth, and ribose is a key piece of evidence.
  • The fact that sugars can survive in space shows us that they could have originated anywhere.

    The first known evidence of sugars on a meteor has been found by researchers from Japan and from NASA’s Goddard Space Flight Center, NASA reports. The research team says that the combination of these sugars with previously discovered materials like amino acids could mean that all the building blocks of the beginning of life on Earth originated in space. The team specifically found ribose, which is the ribo in ribonucleic acid (RNA), considered to be older and more foundational than DNA.

    “The team discovered the sugars by analyzing powdered samples of the meteorites using gas chromatography mass spectrometry, which sorts and identifies molecules by their mass and electric charge,” NASA reports. The two meteorites that they dusted into Fun Dip are named NWA 801 and Murchison, and both are heavy in carbon that would also be required for life to begin.

    But that carbon is heavy carbon instead of the “light” carbon we typically see on Earth—think “heavy water” versus water, in both cases meaning the heavy version has larger, heavier molecules. This tells scientists that the carbon portion is strictly from space. Could the sugars have jumped aboard the meteorites when they struck Earth? Scientists don’t think so, and the heavy carbon is a good piece of evidence.

    A model of the molecular structure of ribose sits next to an image of the Murchison meteorite.
    NASA/Yoshihiro Furukawa

    This discovery is not evidence of the wonderful but outlandish theory of panspermia, which posits that actual living things or genetic material came to Earth from somewhere else in space. The truth is likely both more prosaic and more wondrous, because Earth existed for a billion years before any signs of life emerged, during which the critical pieces of chemistry could have arrived at intervals on meteorites. Like the Blues Brothers, they had to wait until the whole band was back together.

    Did all the parts arrive at the same time? Did sugars exist and hang around for millions of years before amino acids finally came, or vice versa?

    The scientists have more meteorites to powder and study, but their immediate next step might reinforce that these sugars are from outer space. Molecules can have a quality called chirality, meaning they come in two versions that are mirrors of each other. These are called left-handed and right-handed molecules. On Earth, all amino acids are left handed, and all sugars are right handed. If the sugars from space are left handed, that will demonstrate their space origins.

    At the end of their paper, the team conclude, “[T]his work provides evidence that prebiotic sugars could have been delivered to ancient environments on the Earth and possibly on Mars.” Mars is very like Earth in many ways but its smaller mass and colder orbit means it could have run out of any geothermal juice a long, long time ago, missing the viability window for life that developed on Earth.

    The scientists also explain that finding intact ribose and other sugars after some amount of time traveling through space shows that these molecules are capable of making that trip and “surviving” it in the chemical sense. And their discovery of much more ribose than of any deoxyribose (the D in DNA) points to the theory that RNA is in fact the ancestor of DNA.

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