February 24, 2014 | 4
The solar system is full of bits and pieces, remnants of its heyday of activity 4.5 billion years ago. Planets are the most noticeable fossil leftovers, with giant Jupiter being two and a half times more massive that the sum total of the other major worlds. There’s also a vast assortment of far smaller bodies, from asteroids to cometary nuclei, all swirling around the Sun in a variety of orbits.
Perhaps the best known are the diminutive members of the Asteroid Belt, a great zone between the orbits of Mars and Jupiter where millions of objects reside. Altogether they amount to less than a few percent of the mass of the Moon, most are tiny, measured in meters, but a few are large enough to step into the near-planetary club, like the dwarf planet Ceres at nearly 1,000 kilometers across.
Despite their numbers, the members of the asteroid belt are still a remarkably dispersed crowd. Take your spacecraft from Mars to Jupiter and you’d be hard pressed to pass within even a million kilometers of an asteroid, so it can be tough to visualize the grander architecture of this population.
Unless, that is, you take the results of the Sloan Digital Sky Survey (SDSS) and render the locations and motions of 100,000 asteroids detected by its telescopic mapping. The movie here was generated by Alex Parker from SDSS data, and each of the objects is colored to reflect the actual variation in hue of the asteroids, a key to the nature of their composition. Darker (purplish) objects are ‘C-type’ or carbonaceous bodies, while lighter ones are generally ‘S-type’ or ‘V-type’, rocky bodies with lots of silicates.
You can also spot the (reddish) Trojan asteroids – objects lurking in Jupiter’s orbit, ahead and behind of it. This map is a wonderful, sweeping visualization of an important piece of our interplanetary neighborhood. The ‘belt’ of asteroids is thick, not confined to a thin band, orbits are strongly tilted, bodies belong to groups and families – the signs of earlier events, collisions, and gravitational hijinks. The precise composition of objects, and how that composition varies with position, is also a vital clue to the early history of the solar system, a record of earlier turbulence and rearrangement.