Earth-forming ancient rock back after deep space sojourn
London:It may give you goosebumps but researchers now report that an ancient rocky body from Earth's formation has returned after billions of years in cold storage somewhere in deep space.
The celestial body - C/2014 S3 which is more than just a contemporary asteroid that strayed out - is one of the potential building blocks of the rocky planets such as the Earth.
It was expelled from the inner solar system and preserved in the deep freeze of the Oort Cloud for billions of years, said lead author Karen Meech from the University of Hawaii's Institute for Astronomy.
The Oort cloud is a huge region surrounding the sun like a giant, thick soap bubble. It is estimated that it contains trillions of tiny icy bodies.
“We have found the first rocky comet and we are looking for others. Depending how many we find, we will know whether the giant planets danced across the solar system when they were young, or if they grew up quietly without moving much,” added study co-author Olivier Hainaut from ESO in Garching, Germany.
This ancient body was formed in the inner solar system at the same time as the Earth itself but was ejected at a very early stage.
“We already knew of many asteroids but they have all been baked by billions of years near the Sun. This one is the first uncooked asteroid we could observe: it has been preserved in the best freezer there is,” noted Meech in a paper forthcoming in the journal Science Advances.
“C/2014 S3” was originally identified by the Pan-STARRS1 telescope as a weakly active comet a little over twice as far from the Sun as the Earth.
Its current long orbital period (around 860 years) suggests that its source is in the Oort Cloud and it was nudged comparatively recently into an orbit that brings it closer to the Sun.
The team immediately noticed that C/2014 S3 (PANSTARRS) was unusual, as it does not have the characteristic tail that most long-period comets have when they approach so close to the Sun.
A careful study indicated that it is typical of asteroids known as S-type which are usually found in the inner asteroid main belt.
“It does not look like a typical comet which are believed to form in the outer solar system and are icy, rather than rocky. It appears that the material has undergone very little processing, indicating that it has been deep frozen for a very long time,” the authors said.
The object is probably made of fresh inner solar system material that has been stored in the Oort Cloud and is now making its way back into the inner solar system.
The discovery opens up another rich vein in the study of the origins of the solar system.