Image: Amalthée taken in 1999 by the Galileo probe.
Amalthea is one of the moons of Jupiter, the largest planet in the solar system. Discovered in 1892 by American astronomer Edward Emerson Barnard, Amalthea has several features that make it a fascinating and unique moon.
First, Amalthée is distinguished by its small size. With a diameter of around 168 kilometers, it is one of Jupiter's smallest moons. This modest size gives it an irregular and flattened shape, probably resulting from its rapid rotation and weak gravitational field.
Another remarkable feature of Amalthea is its unusual orbit. It orbits very close to Jupiter, at an average distance of about 181,000 kilometers, which places it inside the giant planet's main dust ring. Because of this proximity, Amalthea completes an orbit in less than 12 hours, making it one of Jupiter's fastest moons.
The surface of Amalthea is covered with craters, testifying to the constant impact of space debris. Due to its low gravity, debris thrown up by impacts can easily escape the moon's pull, contributing to the formation of Jupiter's ring.
An interesting feature of Amalthea is its reddish color. This coloring is the result of constant irradiation by charged particles from the solar wind and cosmic rays, which change the chemical composition of its surface and give the moon its distinctive hue.
Also, Amalthea could play an important role in the formation of Jupiter's ring. Debris escaping from its surface could help feed it particles, creating a dense zone of rings around the giant planet.
In sum, Amalthea, Jupiter's small moon, has several intriguing features that make it an exciting subject of study for astronomers. Its modest size, its orbit close to Jupiter, its surface dotted with craters, its reddish coloring and its possible role in the formation of the ring of the planet make it a fascinating research subject to better understand the processes at work in extreme lunar and planetary environments.
| Moons of Jupiter | Diameter (km) | Mass (kg) |
| Ganymede (Jupiter III) | 5262 | 1.5×1023 |
| Callisto (Jupiter IV) | 4821 | 1.1×1023 |
| Io (Jupiter I) | 3643 | 8.9x1022 |
| Europa (Jupiter II) | 3122 | 4.8×1022 |
| Amalthea (Jupiter V) | 262x146x134 | 2.1x1018 |
| Himalia (Jupiter VI) | 170 | 6.7×1018 |
| Thebe (Jupiter XIV) | 110x90 | 1.5x1018 |
| Elara (Jupiter VII) | 86 | 8.7×1017 |
| Pasiphae (Jupiter VIII) | 60 | 3.0×1017 |
| Carme (Jupiter XI) | 46 | 1.3×1017 |
| Sinope (Jupiter IX) | 38 | 7.5×1016 |
| Lysithea (Jupiter X) | 36 | 6.3×1016 |
| Ananke (Jupiter XII) | 28 | 3.0×1016 |
| Adrastea (Jupiter XV) | 20x16x14 | 0.2x1016 |
| Leda (Jupiter XIII) | 16 | 0.6×1016 |
| Callirrhoe (Jupiter XVII) | 9 | 0.087×1016 |
