Amalthea is a small, irregularly shaped moon of the planet Jupiter. It was discovered in 1892 by the astronomer Edward Barnard and is one of the largest moons of Jupiter, measuring about 250 kilometers (155 miles) in diameter. Amalthea is primarily composed of water ice and rock, giving it a reddish color due to the presence of organic compounds. The moon orbits Jupiter at a distance of approximately 181,000 kilometers (112,000 miles) and completes a rotation in about 12 hours. Amalthea is part of a group of moons known as the Jovian moons, which includes other notable moons like Io, Europa, and Ganymede. Its unique shape and surface features make it an interesting subject for scientific study.