Scientists have found an asteroid that may have been an ancient baby planet, formed when the earth was only in its infancy.
The European Space Agency’s probe Rosetta flew past the asteroid Lutetia last year, between Mars and Jupiter and they have studied it closely with spectroscopic and thermal sensors. They found that this is a rare find indeed – being a primitive ‘mini planet’ that was once round may have tried to form a planet. Astronomers say that Lutetia should be called a ‘planetesimal’, meaning a body formed from clumps of cosmic grains.
This asteroid is possibly the only example we have of a primitive body, meaning it dates all the way back to the birth of our solar system. So far, all the other objects in the asteroid belt appear to be fragments of larger bodies that have broken apart a very long time ago. Lutetia looks to have been around for 3.6 billion years and once tried to form a molten iron core, just like a planet.
The ESA say “The density implies that Lutetia contains significant quantities of iron, but not necessarily in a fully formed core. To form an iron core, Lutetia would have had to melt as a result of heat released by radioactive isotopes in its rocks. The dense iron would then sink to the centre and the rocky material would float to the top.
However, VIRTIS indicates that Lutetia’s surface composition remains entirely primordial, displaying none of the rocky material expected to form during such a molten phase. The only explanation appears to be that Lutetia was subjected to some internal heating early in its history but did not melt completely and so did not end up with a well-defined iron core.”
Rosetta project scientist Rita Schulz said “We picked a most important member of the asteroid belt. All the asteroids encountered so far were different from each other, but Lutetia is the only one in which both primordial and differentiation features have been found. These unexpected results clearly show that there is still much more to investigate before we understand the belt fully.”