NASA's Trojan asteroids-bound Lucy spacecraft has safely passed the asteroid Dinkinesh marking a major milestone in the mission, NASA has announced. As a small main belt asteroid, Dinkinesh is not one of the prime targets of the mission, but that’s no reason to pass up whatever information a visit can provide. Moreover, the flyby offers a perfect opportunity to test out Lucy’s instruments and fine-tune everything for the main events. However, it will be around a week before we start getting any images of its first successful flyby.
The Lucy mission, named after the unfortunate human ancestor that revolutionized paleontology, is to explore Jupiter’s Trojan asteroids. The space rocks, named after heroes of the Trojan War, co-orbit the Sun with Jupiter, traveling approximately 60 degrees ahead or behind it in its orbit, technically known as Jupiter’s Lagrangian points L4 and L5.
Although Jupiter’s mighty gravity has pulled a lot of asteroids into its orbit, they’re thought to be less densely packed there than in the main asteroid belt and consequently are expected to have experienced fewer collisions. This should make them better time capsules of the Solar System’s early formation, and therefore priority targets to study.
On the other hand, not all Trojans look the same, even at this distance, raising the possibility of differing origins. By visiting at least six of them, Lucy may help us work out which ones come from where.
It’s a long way to Jupiter’s orbit, however, and after launching two years ago Lucy won’t encounter its first Trojan until 2027. In the meantime, the apparently ordinary asteroid Dinkinesh was close enough to its path that Lucy could divert to pass it without expending too much fuel.
As intended, Lucy passed 430 kilometers (270 miles) from Dinkinesh. The encounter, occurring at relative speeds of 4.5 km/s (10,000 mph) was a lot faster than is intended for Lucy’s main targets.
We should get images of this encounter in a round a week. “The team has determined that the spacecraft is in good health and has commanded the spacecraft to start downlinking the data collected during the encounter. It will take up to a week for all the data collected during the encounter to be downlinked to Earth," according to a post on the Lucy Mission blog.
The reason we have to wait for the data is that, in order to maximize observations, Lucy was reorientated two hours before the closest passage, so its high-gain antenna was pointed away from Earth. Images were stored and will be sent back on delay.
Dinkenesh is considerably smaller than Lucy’s Trojan targets and will test the spacecraft’s capacity to return high-quality images of something so small.
Meanwhile, in other asteroid mission news, plans have been published for the future of OSIRIS-REx, fresh from its successful dropping of a sample of asteroid Bennu on Earth. An open access paper in the Planetary Science Journal details the already announced plans for the renamed ORIRIS-APEX to voyage on to encounter Apophis, considered the asteroid with the highest chance of striking Earth in the next two centuries.