Titan: bright enough to be seen in a Wal-Mart telescope 1944: discovery that spectrum had absorption lines of methane: a moon with an atmosphere. Known to be about twice the mass and about 50 percent larger in diameter
Inferences about the surface of Titan
25 years later…another spacecraft on a mission
Concept of the Huygens lander…an artist’s conception
Pictures of Titan from the approaching Cassini spacecraft
A new view of Titan (from close up)
Titan has flow channels, too
On the surface
Cassini radar shows lakes of methane
Recent observations from Cassini show different manifestation of methane lakes: sunlight glints from the lake surfaces
Reasons for the interest and importance of Titan: it has a dense atmosphere and a “hydrological cycle” based on another compound. Despite its alien nature, in some ways it is the most Earth-like object in the solar system
The surface of Titan: an artist’s view
Another moon of Saturn: Enceladus Diameter=500km Mass = 0.0012 that of Earth’s Moon Orbital period=1.37 days Semimajor axis of orbit=238,000 km
Cassini gives a closeup view of Enceladus
Why Enceladus is of interest
Enceladus: another case in which subsurface water flows up through cracks to the surface of the object
Summary: several moons of the outer planets, in addition to being amazing natural spectacles, may be abodes for primitive forms of life, or at least give us some insight into the astro-biochemical processes which gave rise (or didn’t) to life. Future spacecraft will have much to explore. Stay tuned.
Dostları ilə paylaş: |