(pic of Lutetia courtesy of European Space Agency Rosetta Probe)
One of the things that makes the Earth habitable, with it’s nice toasty orbit rather near our local star is the magnetic field that deflects a lot of the Solar wind that blows this way. Those charged particles are and the magnetic field are what give us the Aurora’s in our Northern and Southern skies.
The reason we have such a field is that the Earth has a molten core that is spinning and that produces the magnetic field that protects us. Now it looks as though we have found an asteroid that at one point probably had a field just like the Earth’s.
There is an asteroid called Lutetia. It is one of the main body asteroids orbiting between Mars and Jupiter. It is rather big such bodies go, being 75 miles, by 63 miles, by 47 miles. What makes it unique is that it is so dense it tends to indicate that it might have a metallic core like the Earth did.
Space.com is reporting that the density has been discovered by data from the Rosetta probe crafts OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) instruments.
By taking pictures of the asteroid and studying how its gravitational field bent the radio waves around it a team from the European Space agency (who are sending Rosetta to visit a comet further out in the Solar System) where able to determine that it has a density around that of a diamond or 212 pounds per cubic feet.
This is as dense as an asteroid, or nearly any body in the Solar System gets. Combined with the obvious cratering on the surface they have proposed that it might indeed be like the Earth.
Our molten core was formed by the accretion process that most planets formed through. We had a bit of extra help in the form a Mars size object that was probably co-orbiting with the early Earth and eventually caught up and impacted forming both our planet and the Moon.
All that mass slamming together made for a very hot planet where the denser elements like iron and nickel moved the middle and the lighter elements tended to stay on the surface. Between the pressure of the other matter and the heat of the impact billions of years later we still have a molten core that spins and provides us our magnetic field.
Now, the article keeps implying that Lutetia might still have a molten core, but to me that is a major mistake. While the asteroid is as big a nice sized mountain range, it is not in any way big enough to have the core still be molten after 4.5 billion years.
The theory for the density is that it too formed by smaller bodies smashing together in the early days of our Solar System. That would have allowed the same process that formed the Earths core to move dense material inward and leave a porous and lighter crust.
But there is a lack of pressure in the form of gravity and the over all heat in forming something that size versus the Earth is much smaller. So the likelihood of it still having a molten core strikes me as exceptionally small.
This is especially when one considers that Mars core has probably cooled and stopped spinning, depriving that planet of the protective magnetic field. Lutetia is not even close to the size of Mars.
Still if it turns out that this asteroid did have a molten core at one time it could answer a question that has been troubling astrophysicists for decades. Namely how is it possible that some of the meteoroids that make it to the Earth are magnetized? From the article:
"The origin of this magnetization has been a key unsolved problem for nearly five decades," Weiss said. "If asteroids are partially differentiated, they could have formed molten metallic cores that generated ancient magnetic fields. These fields could explain the magnetization observed in many kinds of primitive meteorites."
Now that we have found one asteroid that is dense enough to support this kind of theory we will be on the look out for more. All of this will help us to refine our understanding of the formation of our Solar System and others.
Just one last thought, this was all discovered as a side project to a completely different mission. Think about the numbers of amazing things that there might be to learn lurking out there in the cold dark of our own Solar backyard!
The floor is yours.