Hi, I’m Marley, the astronomer here at the Space Centre. This month we are looking at the science behind science fiction, which means I get to talk a bit about Star Wars. If you haven’t seen The Empire Strikes Back, some minor spoilers are going to follow below.

After the events of A New Hope, our favourite rebels have set up base on Hoth, a planet of snow and ice. Darth Vader and the Imperial forces find them, and our heroes have to escape from Hoth. However, our heroes onboard the Millennium Falcon are not able to jump to lightspeed to escape – the hyperdrive has been damaged! Instead, they are forced to flee to an asteroid field. The field is densely packed with asteroids that are moving very quickly. They collide with TIE fighters, take out a star destroyer, and even collide with each other. Eventually, the Falcon lands inside a cavern on one of the larger asteroids. Except it isn’t a cavern at all – the crew has landed inside the mouth of a giant space slug!

Luckily for us, our asteroid belt is very different from the one depicted in The Empire Strikes Back. Our main asteroid belt is far less dense. Current estimates put the asteroid count at just over a million between the orbits of Mars and Jupiter. It sounds like a lot, but if we were to combine the total mass of the asteroids, it would be less than that of the Moon. Most of them are pretty small, with the smallest being less than 10 meters in diameter, and the largest being 530 kilometres in diameter. Because the asteroid belt covers such a large physical area, the chances of a spacecraft hitting one is less that one in a billion. Spacecraft are launched through the asteroid belt quite often. The first was Pioneer 10 in 1973, and the next spacecraft to do it will be the Juice spacecraft as it travels to Jupiter. Juice will pass through the asteroid belt twice!

Really, the only way a spacecraft will encounter an asteroid is if it is aimed towards one. A well known asteroid specific mission is NASA’s OSIRIS-REx mission. This spacecraft travelled to asteroid Bennu.  It collected a sample from the surface (no space slugs spotted), and is now on its way back to deliver that sample back to Earth. Scientists expect that sample to arrive September 24th 2023!

Another mission that has collected a sample from the surface of an asteroid is JAXA’s Hayabusa2 mission. This spacecraft studied asteroid Ryugu, collecting samples from the surface and delivering them back to Earth in December of 2020. Scientists are currently studying these samples, and in March 2023, they published a paper detailing that the samples contain thousands of different organic molecules – carbon based molecules. These include amino acids, and other minerals found indicate that they would have formed in the presence of water.

The asteroid field that we see in Empire Strikes Back serves for a high stress environment, but is not what we expect to see in our galaxy. Though I’m okay with space slugs living in a galaxy far, far, away.

Check out some asteroid themed activities below.