Note4Students
From UPSC perspective, the following things are important :
Prelims level: Mimas, Cassini Mission
Mains level: NA
Introduction
- Recent findings published in the journal Nature suggest that beneath the icy shell of Mimas, there lies a potential liquid ocean, challenging previous assumptions about the moon’s composition and internal dynamics.
About Mimas
| Description |
|
| Discovery | Discovered by William Herschel on September 17, 1789. |
| Characteristics | Smallest and innermost of Saturn’s major moons. |
| Size | Diameter of about 396 kilometers (246 miles), making it one of the smallest known astronomical bodies that is rounded in shape. |
| Features | Known for its large Herschel Crater,
Called as “Death Star” from the Star Wars films. |
| Composition | Mostly composed of water ice with a small amount of rock. |
| Orbit | Orbits Saturn at a distance of about 185,520 km (115,220 miles). |
| Exploration | Visited by the Cassini spacecraft, which captured detailed images of its surface during its mission to Saturn. |
Astronomical Insights
- Potential Liquid Ocean: Scientists analyzed Mimas’s orbital motion using data from NASA’s Cassini spacecraft, concluding that the moon’s oscillations indicate the presence of either an elongated silicate core or a global ocean.
- Librational Model: Calculations based on Mimas’s librations and orbital changes reached a deadlock, prompting consideration of a subsurface ocean. Theoretical models incorporating viscoelastic outer layers and hydrostatic interior interfaces suggested an ice shell thickness of 20-30 km.
- Surface Heat and Eccentricity: Estimates indicate surface heat release of approximately 25 milliwatts per sq. m, expected to reduce Mimas’s eccentricity by half in 4-5 million years. Simulations suggest the ocean may have formed 2-25 million years ago, with potential hydrothermal activity.
Implications and Findings
- Comparative Analysis: Similarities between Mimas and Enceladus, another Saturn moon with a global ocean, hint at potential hydrothermal activity despite surface differences.
- Ice Shell Composition: The viscoelastic nature of Mimas’s outer icy layer and hydrostatic interior interfaces align with observations, supporting the theoretical ice shell thickness determined through calculations.
Get an IAS/IPS ranker as your 1: 1 personal mentor for UPSC 2024
