Asteroid spotting

This is Dawn. And she’s a much underrated spacecraft. Launched back in 2007, Dawn’s mission is fascinating but, to many people, not especially glamorous.

You see, in 2011 Dawn arrived at her new home in the asteroid belt. With her solar arrays measuring nearly 20 metres when fully extended, and equipped with high tech xenon ion propulsion, Dawn is an impressive piece of machinery. Those ion thrusters make Dawn capable of a velocity change of over 10 km/s – a lot more than any other craft to date. Which is necessary for our first proper ambassador to the asteroids.

A little over a year ago, on July 11th 2011, Dawn entered into orbit around the asteroid Vesta – the second largest object in the asteroid belt, accounting for around 9% of the belt’s total mass. With an average diameter of 525 km, Vesta is an interesting object. Asteroids aren’t normally thought of in terms of geology, but Vesta is known to have been resurfaced due to past geological activity. This animation of Vesta’s rotation also shows a series of concentric equatorial grooves encircling the big rock. Interestingly, they’re likely to be compression fractures created during a past impact, and they’re some of the longest canyons in the entire solar system.

Being the most reflective asteroid known, you can even sometimes see Vesta with the naked eye, provided you’re watching from suitably dark skies. At its brightest, its magnitude can reach +5.4!

But Vesta is only the first target. on August 26th this year (a little under two weeks from now), Dawn is set to be on the move again, headed for her final destination – the dwarf planet Ceres. Interestingly, Dawn is expected to arrive at Ceres by sometime in February 2015, shortly before New Horizons arrives at Pluto. This will make Ceres the first dwarf planet to be studied up close and personal.

Ceres and Vesta are interesting objects. Much more than just hunks of space rock, they’re believed to be protoplanets – the last ones remaining. Think of them as the fossilised cores of planets which never formed. Interestingly too, they’re both very different little objects, suggesting that before they both ended up in the asteroid belt, they may have formed in different parts of the solar system.

I must say, I can’t wait for Dawn to arrive at Ceres and start taking a closer look at the would-be planet. In 2015, we get to see two dwarf planets in the same year. You can’t tell me that isn’t exciting. Safe travels, Dawn!

Image credits: All images courtesy of NASA/JPL

About Invader Xan

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
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