How planets like Earth formed remains a bit of a mystery. Most of our ideas revolve around clumps of rock slowly joining together, whether that’s one growing rock picking up others or multiple large chunks joining together.
A new study, however, proposes a different theory. Published in the journal Science Advances, it suggests that giant balls of warm mud may have spawned our world (and others), not rocky asteroids. Go figure.
“The assumption has been that hydrothermal alteration was occurring in certain classes of rocky asteroids with material properties similar to meteorites,” study co-author Bryan Travis from the Planetary Science Institute in Arizona said in a statement.
“However, these bodies would have accreted as a high-porosity aggregate of igneous clasts and fine-grained primordial dust, with ice filling much of the pore space. Mud would have formed when the ice melted from heat released from decay of radioactive isotopes, and the resulting water mixed with fine-grained dust.”
To explain that a bit, the scientists are proposing that under certain concentrations of ice, dust, and rounded particles called chondrules, early asteroids in the Solar System may not have lithified. In other words, they may not have become rock.
Instead, they would have begun life as balls of mud, according to the computer model devised by the researchers. Ice that had melted by decaying radioactive atoms in the dust and gas would have turned the composition into mud. This could explain certain chemical and thermal details we see on asteroids.
By smashing together, or via other processes, these balls could have solidified over time – creating things like our planet. But in the heart of some asteroids, these original balls of mud may still exist, if temperatures at their hearts are above freezing.
In particular, this research focuses on carbonaceous asteroids, which are dark in color and make up 75 percent of asteroids in our Solar System. Consisting of fine particles suspended in water and kept warm by radioactive elements, these may have looked very much like the mud you might imagine, before solidifying.
“The results showed that many of the first asteroids, those that delivered water and organic material to the terrestrial planets, may have started out as giant convecting mud balls and not as consolidated rock,” the statement notes.
Upcoming missions, like NASA’s OSIRIS-REx and Japan’s Hayabusa 2, may give us further information on this by directly sampling asteroids and bringing material back to Earth.