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Small Gray Dots

A spacecraft designed to investigate ancient asteroids near Jupiter will reach those distant targets with a little help from Earth. NASA’s Lucy spacecraft is using Earth’s gravity to help propel it beyond Mars. In the process, its cameras have captured captivating images of our home planet.

The Terminal Tracking Camera (T2CAM) on Lucy acquired this image of Earth and the Moon on October 13, 2022. At the time, the spacecraft was 890,000 miles (1.4 million kilometers) from Earth—almost four times the distance from the Earth to the Moon.

The image was acquired during an instrument calibration sequence as Lucy approached Earth for the first of the mission’s three gravity assists. These slingshot maneuvers around Earth will give Lucy the energy it will need to reach the Trojan asteroids—a group of asteroids trapped in an orbit at the same distance from the Sun as Jupiter. The icy rocks are thought to be ancient relics from the early solar system, which formed 4.5 billion years ago. But these “fossil” asteroids have never been studied up close.

The second image was acquired on October 15, 2022, when the spacecraft was 380,000 miles (620,000 kilometers) from Earth. That is still greater than the distance between the Earth and the Moon, but close enough to see some familiar features. In this grayscale view, clouds (white) swirl above continents (light gray) and oceans (dark gray).

East Africa is toward the top-left. This is the location of Hadar, Ethiopia, and the discovery site of an early hominin fossil named “Lucy.” Named in recognition of the fossil skeleton’s contribution to understanding human evolution, the spacecraft is expected to advance our knowledge about the origins of our solar system and the formation of its planets, including Earth.

On October 16, 2022, the spacecraft passed within 220 miles (350 kilometers) of Earth—closer than the orbit of the International Space Station. The close encounter with Earth put Lucy in a zone with satellites and debris. The Lucy team accounted for the hazard and had pre-prepared several collision avoiding maneuvers.

A second Earth-gravity assist in 2024 will propel Lucy through the solar system’s main asteroid belt between the orbits of Mars and Jupiter, and toward one of two swarms of Trojan asteroids that share an orbit with Jupiter. A third gravity assist in 2030 will send Lucy toward the second group of Trojan asteroids.

Images courtesy of NASA’s Goddard Space Flight Center (GSFC) and the Southwest Research Institute (SwRI). Story by Kathryn Hansen based on materials from GSFC/SwRI.

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