Lucy's wild ride to Jupiter's orbit… but not to Jupiter
In a little less than a month, NASA will launch an ambitious mission through the asteroid belt and out to Jupiter’s orbit. The spacecraft won’t be visiting Jupiter, though: It will fly by several asteroids that share an orbit with the giant planet, looking to investigate these fossils from the solar system’s early days.
This mission is called Lucy, named after the skeleton of Australopithecus afarensis, a hominin dating to over 3 million years ago, an early ancestor to humans. The skeleton itself was named after the Beatles song “Lucy in the sky with Diamonds”, making this circuitous naming path come full circle.
Drawing schematically showing the positions of asteroids in Jupiter’s L4 (top left) and L5 (bottom) points. These asteroids are dark and slightly reddish, and may be leftover from the formation of the solar system. Credit: NASA/JPL-Caltech
Lucy’s main mission is to visit what are called Jupiter’s Trojan asteroids and investigate them with a suite of scientific instruments. Due to a quirk of orbital physics, when something like a planet orbits a star there are several points along and near that orbit where there are gravitational stable spots; if you place a small object there it will orbit the star stably as well. These are called Lagrange points, and are pretty useful for space missions (James Webb Space Telescope, due to launch in December, will orbit around the Sun near one of Earth’s Lagrange points).
