NASA's Lucy mission executed the first of three planned slingshot maneuvers around Earth this month in preparation to study Jupiter's Trojan asteroids, but the spacecraft made sure to take some stunning photos of Earth and the moon before retreating into deep space.
The images, taken on Oct. 13 and Oct. 15 as Lucy began its approach toward Earth for a gravity-assisted speed boost on Oct. 16, are more functional than a couple of simple snapshots. The images were taken to help calibrate Lucy's Terminal Tracking Camera (T2CAM) system, which features two identical cameras that the spacecraft will use to pinpoint and track target asteroids as it zips past at high speeds.
The first image, taken on Oct. 13, highlights the incredible distance between the Earth and the moon. At the time, the two bodies sitting at opposite edges of the frame were about 890,000 miles (1.4 million kilometers) away from Lucy, according to a NASA statement. Mission personnel also intended to have the spacecraft photograph the moon on its way back into deep space.
The second photo, snapped two days later, is a close-up shot of the Earth as Lucy approached, taken at a distance of roughly 380,000 miles (620,000 km). In the image, Hadar, Ethiopia, is just visible on the left-most edge of the planet, giving Lucy (and us) a cosmic-eye glimpse of the spot where the 3.2-million-year-old human ancestor fossil for which the mission is named was discovered.
Lucy will be making three flybys of Earth in total, using Earth's gravity on its approach to speed itself up so it can start its years-long voyage to Jupiter's Trojan asteroids. During the first flyby, Lucy came within just 220 miles (350 km) of the Earth's surface — a lower altitude than the International Space Station and many satellites and close enough for sharp-eyed skywatchers on the ground below to spot it.
Lucy will be the first spacecraft to visit Jupiter's Trojan asteroids, so named because they orbit the sun at the same distance as Jupiter, both in front of the planet and behind it. They occupy two of the five Lagrange points of Jupiter, the only locations where a stable orbit so close to the gas giant is possible.
During its 12-year mission, Lucy is set to fly by nine asteroids, including one in the main asteroid belt, to study their composition, density and diversity. While that's an impressive number of asteroids to study in one go, there are as many as 12,000 Trojan asteroids orbiting with Jupiter, according to the International Astronomical Union. Scientists believe these rocks are 4-billion-year-old "fossils" left over from the formation of the solar system.