Scientists have found liquid water trapped in crystals in rock samples returned from the asteroid Ryugu, about 300 million km (186 million miles) from Earth.
Samples of the asteroid were found to contain a range of minerals, including calcium- and aluminum-rich particles, magnetic minerals such as magnetite, as well as carbonated water containing salts and organic matter.
The samples were returned to Earth in 2020 for analysis by the Japan Aerospace Exploration Agency (JAXA) Hayabusa2 mission.
The findings, published in the journal Science offer more evidence on Friday to support the theory that life — or life precursor molecules — may have originated on Earth from space.
“Liquid water trapped in crystals in the sample was found. The water was held in micron-sized holes,” JAXA said in a statement.
In the study, scientists analyzed 17 Ryugu samples measuring about 1-8 mm and found an iron sulfide pyrrhotite crystal containing carbonated water.
Researchers suggested that the parent space rock from which the Ryugu asteroid descended was born in the darkness of a stellar cloud of gas that is far from the reach of the sun’s light.
In this parent body, they said there would be variations in the ratio of water to rock between the surface and the interior, with rocks deeper underground holding more water.
Simulations conducted by the scientists suggested that Ryugu’s parent body accumulated about 2 million years after the formation of the solar system and then heated to about 50°C over the next 3 million years, resulting in chemical reactions between water and rock.
The asteroid samples were found to contain some material near the surface of the parent body before the impact’s destruction and some of the interior of the parent space rock.
Scientists compared the hardness of the samples to that of volcanic igneous rocks on Earth, which softened them and made them easy to cut with a knife.
Researchers found a diverse array of minerals in these rock fragments, the differences of which, they said, could be explained by the different conditions for chemical reactions with water.
Scientists said the hydrous minerals, including silicates and carbonate compounds discovered in the asteroid sample, likely formed when raw materials in the parent body reacted with water and carbon dioxide inside the giant space rock.
Based on the condition and stability of some of these minerals, researchers said the water temperature in some parts of the parent rock was about 25C.
Other studies have also suggested that the magnetite iron minerals in the Ryugu samples formed “surprisingly low” temperatures below 40°C.
The new analysis also revealed that “coral-like crystals” grew from Ryugu’s liquid water.
Based on these findings, researchers said an environment “similar to Earth’s oceans” existed in the interior of Ryugu, adding that such aquifers are more widely distributed in the solar system than anhydrous objects.