How to make an asteroid using sunlight

In the main belt, collisions are often responsible for the asteroid families we see. But collisions are typically violent events, while the orbits of Mars’ Trojans indicate a gentler origin. Based on this evidence, Christou’s team believes that solar radiation pressure — that is, the pressure exerted on a body by the energetic photons in sunlight — caused Eureka to spin faster and faster over time. “Eventually there comes a time where all the bits that make up the asteroid cannot stay together and start flying off,” Christou said in a press release. This effect is actually quite well known as the Yarkovsky-O’Keefe-Radzievskii-Paddack effect, or YORP effect, for short.

Mars’ other two Trojans haven’t undergone the same rotational speed-up. One is already rotating fairy chaotically; Christou explained that because the YORP effect is small, the asteroid’s tumbling overpowers and nullifies it. The other Trojan lies close to the orbital zone of stability that keeps Trojans in place; any small bits spun off by the YORP effect would likely go sailing off into unrelated orbits, rather than stick around as fellow Trojans. Thus, sunlight’s effects could not only create, but also destroy or prevent asteroid families from forming.

Learning more about Mars’ Trojans offers two major benefits. First, “These could be resources for trips to Mars," says Christou. “If they have hydrated minerals then you can exploit those for fuel.” And second, the YORP effect could also impact asteroids near Earth, helping to explain the origin of several near-Earth asteroid pairs and triplets and improving our understanding of the rocky occupants that share the space closest to home.

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http://www.astronomy.com/news/2017/10/how-to-make-an-asteroid-using-sunlight