So far, researchers have found many signs of the building blocks of life in space, but what exactly have they discovered, and what remains to be found?<\/p>\n
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Scientists have discovered the basic ingredients for life in asteroids and meteorites, on Mars, and around young stars. All of those findings have come in the past few years, and upcoming missions aim to search for these building blocks of life.<\/p>\n
But how many building blocks of life have we found in space so far?<\/p>\n
First, it's important to define what we mean by the building blocks of life. Scientists are looking for molecules that look like those found in life on Earth, including proteins; RNA; and lipids, the fatty molecules that make up cell membranes.<\/p>\n
We\u2019ve found many on sample-return missions. The asteroid Bennu, brought back to Earth in 2023, contained all five nucleobases of DNA and RNA, along with 14 of the 20 amino acids used by living organisms. Its sibling asteroid Ryugu also yielded all five nucleobases, including uracil, which is found in RNA.<\/p>\n
Other techniques, like radio astronomy, look for these building blocks in distant regions of space.<\/p>\n
Astronomers categorize the molecules they find by complexity, starting with a broad group called "complex organic molecules" (COM). These are carbon-containing molecules with six or more atoms. Of the 350 molecules of any kind discovered in space so far, "about 180 of them qualify as COMs," Sergio Ioppolo, an astrochemist and an associate professor in the Department of Physics and Astronomy at Aarhus University in Denmark, told Live Science. "That cutoff is an operational convention rather than a fundamental definition of complexity."<\/p>\n
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Not all COMs are building blocks of life, but some of them are. A subgroup within COMs is a "prebiotic" molecule that scientists think may have played some role in the origin of life. A prebiotic molecule "has no structural rule," Ioppolo said \u2014 different scientists define it slightly differently.<\/p>\n
Ioppolo defined a prebiotic candidate as a molecule whose detection scientists are confident in, that could plausibly form and survive without life already existing, and that has a documented role as a building block, precursor or intermediate in some proposed pathway to life.<\/p>\n
Using that definition, Ioppolo estimates "roughly 30 detected prebiotic candidates, although the exact number depends on where the line is drawn."<\/p>\n
Some of the richest hunting grounds for these molecules are in molecular clouds \u202a\u2014\u202c interstellar regions of gas and dust that are dense enough for molecules to form. Using radio astronomy, Izaskun Jim\u00e9nez-Serra, an astrochemist and staff researcher at the Center for Astrobiology in Spain, and her team have detected more than a dozen prebiotic molecules in molecular clouds at the center of the Milky Way, including the four-carbon sugar erythrulose \u2014 the first true sugar found in space.<\/p>\n
A Hubble image of the Milky Way\u2019s center, in the constellation Sagittarius. Researchers have discovered a sugar found in raspberries buried in a cloud in this region.<\/p>\n
However, there's a limit to the size and complexity of molecules that astronomical surveys can detect. To identify each molecule, scientists analyze the light from molecular clouds, which can reveal which parts of the electromagnetic spectrum have been absorbed. Those "spectral lines" act as a fingerprint for each molecule.<\/p>\n