ESA Science & Technology04-Jul-2005 14:21:59

Saturn's Moons


I - Discovered by Herschell (1789)

Physical Parameters

Orbital Parameters

Radius (km)


Radius (km)

185 520

Mean Density (kgm-3)



22h 37m 05s

Mass (kg)

3.75 x 1019

Velocity (kms-1)


Magnitude (V0)


Rotational Period

22h 37m 05s

Escape Velocty (kms-1)




Mean Surface Albedo


Inclination ( )


Knowledge before Cassini-Huygens

Despite its small size Mimas is spherical, suggesting it is sufficiently plastic to have reformed following each collision. The surface is covered in overlapping impact craters, including the single huge Herschel crater. Herschel is roughly one-third of the size of the satellite at 130 km in diameter, 10 kilometres deep and a central peak 6 kilometres high. The crater was probably formed by an impactor roughly 10 kilometres across. It is thought that an impact by a body only slightly larger would have destroyed the tiny moon.

Other craters across the surface span 2 to 45 kilometres in diameter. The surface also appears to be very ancient with no evidence for recent geological activity, suggesting the craters formed early in the history of the solar system.

*Note: in the following section all images courtesy NASA/JPL/Space Science Institute unless stated otherwise.

26 July 2004

Cassini Instrument: Imaging Science Subsystem

Date: 3 July 2004

Distance: 1.7 million km

Scale: 10 km per pixel

Phase Angle: 102

Image Notes: Narrow angle mode, visible light, Herschel crater showing

29 November 2004

Cassini Instrument: Imaging Science Subsystem

Date: 7 November 2004

Distance: 3.7 million km from Saturn

Scale: 22 km per pixel

Image Notes: Narrow angle camera, combined image in red, green and blue filters

In this portrait, Saturn's moon Mimas is seen against the blue-streaked backdrop of Saturn's northern hemisphere. The part of the atmosphere seen here appears darker and more bluish than the warm brown and gold hues seen in Cassini images of the southern hemisphere, due to preferential scattering of blue wavelengths by the cloud-free upper atmosphere.

27 January 2005

Cassini Instrument: Imaging Science Subsystem

Date: 18 December 2004

Distance: 2 million km from Mimas

Scale: 12 km per pixel

Phase Angle: 105

Image Notes: Visible light, magnified x2, and contrast enhanced.

Mimas is caught beneath Saturn's rings in this view from Cassini. Notable is the brightened outermost edge of the A ring beyond the narrow Keeler gap and the periodic brightening of the thin, knotted F ring.

9 February 2005

Cassini Instrument: Imaging Science Subsystem

Date: 16 January 2005

Distance: ~ 213 000 km from Mimas

Scale: 1.3 km per pixel

Phase Angle: 84

Image Notes: Filtered image, magnified x2, and contrast enhanced

A combination of spectral filters sensitive to ultraviolet and polarized light was used for this view of predominantly the leading hemisphere of Mimas. North on Mimas is up. The large Herschel crater is seen at the terminator.

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