NASAのインスタグラム(nasa) - 11月29日 02時16分

Saturn's icy moon Mimas is dwarfed by the planet's enormous rings. Because Mimas (near lower left) appears tiny by comparison, it might seem that the rings would be far more massive, but this is not the case. Scientists think the rings are no more than a few times as massive as Mimas, or perhaps just a fraction of Mimas' mass. Our Cassini spacecraft is expected to determine the mass of Saturn's rings to within just a few hundredths of Mimas' mass as the mission winds down by tracking radio signals from the spacecraft as it flies close to the rings. The rings, which are made of small, icy particles spread over a vast area, are extremely thin - generally no thicker than the height of a house. Thus, despite their giant proportions, the rings contain a surprisingly small amount of material. Mimas is 246 miles (396 kilometers) wide.

Now in its final year of operations, on Nov. 30, 2016, Cassini will begin a daring set of ring-grazing orbits, skimming past the outside edge of Saturn's main rings. Cassini will fly closer to Saturn's rings than it has since its 2004 arrival. It will begin the closest study of the rings and offer unprecedented views of moons that orbit near them. Even more dramatic orbits ahead will bring Cassini closer to Saturn than any spacecraft has dared to go before.

Credit: NASA/JPL-Caltech/Space Science Institute

#nasa #saturn #moon #mimas #nasabeyond #astronomy #planet #cassini #rings #science

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