The Lutetia asteroid is a planet that never properly formed, according to new scientific research. ESA’s Rosetta spacecraft flew by the asteroid in July, collecting data that suggests Lutetia is what’s called a planetesimal, a body that never quite made it to full planethood.
Astronomers argue that the
planet’s asteroid’s irregular shape has come about after billions of years of being pelted by other asteroids and comets. According to Holger Sierks of Germany’s Max-Planck-Institut für Sonnensystemforschung:
“We don’t think Lutetia was born looking like this. It was probably round when it formed.”
And Fabrizio Capaccioni of Italy’s INAF adds:
“It is striking that an object of this size can bear scars of events so different in age across its surface while not showing any sign of surface compositional variation.”
Further data unearthed by Rosetta suggests the planet has a molten metal heart. Beneath its scarred surface, Lutetia has one of the highest densities of any known asteroid, 3,400 kg per cubic metre. Researchers say this could be a sign the asteroid has a predominantly iron heart, though not necessarily a fully-formed core.
Lutetia, or 21 Lutetia to use its full name, was discovered in 1852, and is the second largest asteroid to have been visited by a spacecraft. The Rosetta probe passed it in July within 3,162 km (1,965 mi).
Rosetta has now left Lutetia far behind. It is currently in hibernation, waiting to begin its journey to a 2014 rendezvous with comet Churyumov–Gerasimenko.