NASA CASSINI MISSION (1997-2017)
Iapetus equatorial ridge (20,000 m - 65,6168 ft) or (20 km - 12, 43 mi)
Saturn planet (Iapetus moon)
1. Iapetus equatorial ridge on 10/09/2007
2. Photomosaic of the Iapetus moon from NASA Cassini Spacecraft on 31/12/2004
Assembled by Matt McIrvin
The mountain
Iapetus is one of the numerous Saturn's moon which has a 10 to 20 kilometers high (20,000 m - 65,6168 ft) ridge above the surrounding plains, running along most of its equator, making them some of the tallest mountains in the Solar System. Iapetus's equatorial ridge was discovered when the NASA Cassini spacecraft imaged Iapetus on 31 December 2004, during the NASA Cassini Mission to Saturn. The ridge forms a complex system including isolated peaks, segments of more than 200 km and sections with three near parallel ridges. There are bright areas on the sides of the equatorial ridge near Iapetus's bright trailing hemisphere, which were already visible in Voyager Missions images appearing like mountains and were nicknamed the "Voyager Mountains". Within the bright regions there is no ridge, but there are a series of isolated 10 km (6 miles) peaks along the equator. The ridge system is heavily cratered, indicating that it is ancient.
The prominent equatorial bulge gives Iapetus a walnut-like appearance.
It is not clear how the ridge formed. One difficulty is to explain why it follows the equator almost perfectly. There are at least four current hypotheses, but none of them explains why the ridge is confined to Cassini Regio.
1. A team of scientists associated with the Cassini mission have argued that the ridge could be a remnant of the oblate shape of the young Iapetus, when it was rotating more rapidly than it does today. The height of the ridge suggests a maximum rotational period of 17 hours.
2. The ridge could be icy material that welled up from beneath the surface and then solidified.
3. Iapetus may have had a ring system during its formation due to its large Hill sphere, and the equatorial ridge could have then been produced by collisional accretion of this ring.
4. The ridge and the bulge could be the result of ancient convective overturn. This hypothesis states that the bulge is in isostatic equilibrium typical for terrestrial mountains.
Source:
The Mission
Cassini sails low over the surface of Iapetus on approach to its close encounter with the enigmatic moon on Sept. 10, 2007. Its flight takes it over the rugged, mountainous ridge along the moon's equator, where ancient, impact battered peaks - some topping 10 kilometers (6 miles) in height -- are seen rising over the horizon and slipping beneath the spacecraft as it flies.Frames used in this movie were acquired with the Cassini wide-angle camera on Sept. 10, 2007, as the intrepid robot soared past Iapetus (1,468 kilometers - 912 miles across), within a few thousand kilometers of the surface. Additional simulated images were inserted between the Cassini images in this movie in order to smooth the appearance of the movement, a scheme called interpolation.
The Cassini mission was launched on October 15, 1997 at 8:43 UTC. This 20 years mission was programmed to end on September 15, 2017 by what is called The Grande Finale.
Source:
- NASA Cassini mission Page at Iapetus