Saturn’s E-Ring Enceladus circles with Saturn’s E-ring and many people believe that the water jets (or plumes) that come from Enceladus actually are the cause of Saturn’s E-ring Numerous mathematical models show that such a ring is unstable, with a lifespan between 10,000 and 1,000,000 years. Therefore, particles composing it must be constantly replenished. Enceladus is orbiting inside this ring, in a place where it is narrowest but present in its highest density.
Geological Features 1.) Silicate Core 2.) Outer water-ice-rich mantle 3.) Plate Tectonics 4.) Diapir 5.) Giant Plumes/Geysers 6.) Tiger Stripes – In south polar regions – Warmest part of planet
Why Enceladus? In May 2011 NASA scientists at an Enceladus Focus Group Conference reported that Enceladus "is emerging as the most habitable spot beyond Earth in the Solar System for life as we know it.” Properties: Liquid water, organic carbon, nitrogen [in the form of ammonia], and an energy source. This is key because according to Chris McKay, an astrobiologist at NASA's Ames Research Center, besides Earth, "there is no other environment in the Solar System where we can make all those claims."
The Plumes Dramatic plumes, both large and small, spray water ice out from many locations along the tiger stripes near the south pole of Saturn's moon Enceladus. From right to left, the four major stripes are Damascus, Baghdad, Cairo and Alexandria sulci.
Analysis of Plumes Jack Hunter (J.H.) Waite, of the Southwest Research Institute in San Antonio, Texas and his colleagues say ammonia detected in the jets from Enceladus’ south pole provides the strongest evidence yet for the existence of liquid water beneath the surface. Analyses of Cassini through the heart of the plumes show that 99% of the mass of plume ice-particles is salt-rich. This implies that the water in plume ice came from salty liquid water somewhere beneath the surface, say researchers. Below is the chemical measurement of one of these plumes. This is a chemical measurement contains all of the three things mentioned earlier: Liquid water, organic carbon, nitrogen.
More on Tiger Stripes April 14, 2012- The Fields, Particles and Waves instruments (a.k.a. MAPS) are prime (particularly the ion and neutral mass spectrometer [INMS]) to study the composition, density, three- dimensional structure and variability of plumes; with E-14, and E- 17, this flyby provides good coverage of south polar regions. The Tiger Stripes
How Hot is Hot? -140 F or -90 C May seem cold but is about 270 degrees warmer then the rest of the planet It is formed through a combination of tidal heating and pressurized liquid which then shoots out water vapor and ice particles
Previous Missions Voyager 1 and 2 – Launched in 1977. – Flew by Saturn system in 1980 and 1981, respectively. – First to place Enceladus on the map for possible places of life in our solar system. Cassini – Launched October 15, 1997. – Flown by Enceladus 33 times an average of 34480 km away but with some flybys as close as 25 km. – Most recent just yesterday May 2, 2012.
Voyager 1 and Voyager 2 In the early 1980s, the two Voyager spacecrafts passed Enceladus and found essentially all of the basic background information stated earlier. – 500 km in diameter – Surface reflected almost 100 percent of sun light, etc. Voyager 1 and 2 were important because they catapulted Enceladus to the forefront of prospective places for life in our solar system.
Cassini-Huygens Objectives regarding Enceladus: – Determine the characteristics and geological history of Enceladus – Determine the different physical processes that created the surface of Enceladus – Investigate composition and distribution of surface materials on Enceladus – particularly dark, organic material, and condensed ice – Determine the bulk composition and internal structure of Enceladus – Investigate interaction of Enceladus with Saturn’s magnetosphere and ring system
First Flybys – July 14 & March 9, 2005 During the first two close flybys (175km & 500km) of Enceladus, Cassini discovered a “deflection” in the local magnetic field, and measurements taken pointed to ionized water vapor as the main component. Cassini observed water ice geysers erupting from the south pole, giving credibility to the idea that Enceladus supplies the particles of Saturn’s E ring. It was hypothesized that pockets of liquid water exist near the surface making Enceladus one of the few bodies in the solar system to contain liquid water.
Second Flyby – March 12, 2008 This close flyby (within 50km of the surface) passed through the plumes of Enceladus’ southern geysers and detected water, carbon dioxide, and various hydrocarbons using a mass spectrometer. This flyby also involved mapping surface features that were at a much higher temperature than their surroundings with an infrared spectrometer. A cosmic dust analyzer was intended to be used to collect data, but malfunctioned.
Third Flyby – November 21, 2009 The third flyby came within 1600km of the surface. The composite infrared spectograph (CIRS) was expected to map thermal emission from the tiger stripe Baghdad Sulcus. Data and images returned were expected to help create the most detailed image of the southern part of the moon’s Saturn facing hemisphere and a contiguous thermal map of one of the tiger stripe features. Image of Baghdad Sulcus
May 2, 2012 Flybys are happening continually even as recent as yesterday! This flyby is a radio science (RSS) gravity flyby, which is designed to understand the internal structure of Enceladus, particularly the concentration of mass under the south polar region. RSS will have its usual three periods of observation: two wings and closest-approach. The MAPS pointing will be optimized to gather data near closest approach.
New Discoveries Cassini has been doing wonders for data collection about Enceladus. Information concerning the plumes has all come from Cassini. Infrared imaging has allowed a new model of the interior temperature and design of Enceladus to be made. M ost importantly it has affirmed that there is most likely liquid water on Enceladus, the most important discovery for a planet to potentially have life. NASA provides daily images from Cassini
What Can Be Done? Cassini 2.0 Cassini’s instruments only revealed basic information concerning the prospects of life. New instruments would help confirm findings about the plumes and the hot spots.
Possible Approaches One-way mission: – Multiple flybys of Enceladus and other moons – Crash the orbiter at end of mission – Lander probe (Huygens probe)
Other Approaches Round-trip flight: – More focused mission to collect plume material – Analyze plume material in lab on Earth
Getting there (and maybe back) 1.2 billion km (~8 AU) to Saturn at closest point Cassini: 7 years travel time at up to 45 km/sec Getting there: multiple gravity boosts from Venus, Earth, and Jupiter reduces travel time Requires special alignment of planets; small launch window
Staying there: Engine to slow spacecraft into Saturn’s orbit Steer mainly with Titan flybys Getting Back: More gravity boosts! Extra weight for heat shield, parachute, fuel
Purpose of Cassini 2.0 Assess astrobiological potential and geology of Enceladus Plumes and E-ring: – Confirm liquid water is source of plumes – Look for biomarkers, elements for life – ex: confirm fraction of CO vs. N 2 vs. hydrocarbons Further study of Enceladus surface
Titan Saturn System Mission (TSSM) Joint NASA/ESA proposal for an exploration of Saturn, Titan, and Enceladus Minimum of seven close Enceladus flybys Exploring the composition of the Enceladus plumes and whether the source region is liquid water
Cassini Instruments Optical remote sensing- detect electromagnetic light (infrared, visible, and ultraviolet; low- and high-res) Fields, particles, and waves- study dust (plumes), plasma, and magnetic fields Microwave remote sensing- use radio waves to map atmospheres and surface
Cassini 2.0 Instruments ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) Mass Spectrometer – Reveal chemical composition of Enceladus plumes – Characterize complex organic molecules with a 10× larger mass range, 100× higher resolution, and 1000× better sensitivity than Cassini – Search for biomarkers: carbon-12,- 13 ratio
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