Lecture 33. Cassini-Huygens Mission. reading: Chapter 8

Saturn Pioneer 11 flyby in 1979 V1 in 1980 and V2 in Strong winds up to 1800 kph! Complex Rings and Over 34 Moons. “The Jewel of the Solar System”

Cassini-Huygens Mission Took 7 years and 4 gravity assists (VVEJ) to get there (in 2004). 4 year mission that includes 70 orbits around Saturn and its Moons. Main goals: -measure Saturn’s magnetosphere -up close analysis of rings -composition and dynamics of Saturn’s atm. -map surface of Titan -send Huygens probe to surface of Titan Makes measurements, data sent by high-gain antennae to Earth, picked up by the Deep Space Network, sending Gigabytes of data daily. Powered by 3 RTGs!

Orbiter Instruments Wide angle and narrow angle camera 10 Megapixel CCD sees a quarter 4 km away. Cosmic Dust Analyzer counts dust grains Ion and Natural Mass Spectrometer studies positive ions and neutral particles in upper atm. of Titan and magnetosphere of Saturn Magnetospheric Imaging Instrument first instrument to produce an image of a magnetosphere and ionized gases ( plasma ) Magnetometer Radio and Plasma Wave Science Instrument measures radio signals from Saturn, from interaction of solar wind with Saturn and Titan RADAR uses microwaves to image Titan Radio what is this used for??

Spectrometer splits light into its component wavelengths, fingerprint of compounds present. Mapping component makes a map of where the different compounds are present. Visible and Infrared Mapping Spectrometer bright features: thought the be a volcano

Infrared Spectrometer Measures amount of heat coming from a surface. Cracks of Enceladus 91K (-296˚C) Evaporation of “warm” ice may produce the plume seen. Fractures bluer because they have larger ice crystals

5 different terrains: bright, reflective surface Parts have no craters >35 km Others have no craters Fissures Plains Corrugated terrain Crustal deformations Interior may be liquid Don’t know what the source of heat is! May be tidal heating from orbital perturbations with Saturn, Tethys and Dione.

Ultraviolet Imaging Spectrograph Box of 4 telescopes that can see uv light. Image object, render it in false colors. Shows more ice in the outer part of the rings. Red: dirtier ice, perhaps smaller particles. Found battleship-sized clumps of particles in the rings. Come together and disperse on a daily basis. Can detect H, O, CH 4, water, acetylene, ethane. Collect data as Sun or other stars pass behind Titan. Provides information on composition, temperature, structure of the atmosphere.

Huygens Probe Named after Christiaan Huygens who discovered Titan in Built and designed by ESA. On Dec released from Cassini. 20-day approach toward Titan. Descent slowed by three parachutes, took 2 hours 27 min. Collected data on composition of atmosphere & clouds. Landed near the equator. Survived 1 hr 12 min after landing on the frozen surface.

Huygens Probe Instruments Atmospheric Structure Instrument measures physical properties of the atm, density, wind gusts, waves (if probe landed in an ocean), conductivity of surface Doppler Wind Experiment wind speed during descent Descent Imager/Spectral Radiometer Measures upward and downward flow of light Aerosol Collector and Pyrolyser and GCMS heated aerosols and sent to GCMS, GCMS measured composition of atm. Surface Science Package several sensors to measure physical properties, speed of sound, accelerometer (hard or soft surface), tilt meter

Huygens - General Surface Features Obtained clear images 40 km above the surface. Resembles Earth: - structure of the atm. - meteorology - land forms - fluvial (river) activity Strong evidence for erosion due to liquid flows (possibly methane). Boundary between bright, icy, rugged terrain. and a darker flat area. Dark and bright areas correspond to observations made on the orbiter. Bright areas are higher in elevation. Dark areas appear to drain the light areas into a low-lying dark floodplain. Interpreted as coastline with bright islands. Probe landed on dark area.

Huygens - Surface Spectra of landing site: composed of dirty water ice. Water ice pebbles 3mm-15 cm across. Water ice rocks coated in hydrocarbons. Landed on a solid surface, puff of evaporated methane detected after impact with the warm probe. Also detected from the surface compounds not found in the atm: C 6 H 6, C 2 N 2, CO 2 Suggests complex chemistry occurring on the surface, and different from the atm. Surface wet with methane. Penetrometer: surface consistency of loose wet sand

Huygens - Atmosphere Landing site: 93.7K, 1.47 bars Winds at 120 km were 450 kph Winds at km had a high wind-shear Haze detected all the way down to the surface. Methane at the surface: 5% Relative humidity of methane is 50%. So, unlikely to get methane fogs. Major questions: What is the source of methane? Methane is continually destroyed by photochemical reactions. Where are all the pools of hydrocarbons if photochemistry has been going on for 4.5 Ga?

Huygens - Chemistry Complex organic chemistry confirmed - no new organic compounds found in the atmosphere. May be unidentified organic compounds on the surface. 40 Ar found in the atmosphere - suggests active internal geology

Life on Titan? Do you have the 5 thing needed to have life?

Properties of Water that are Important for Life It is the “universal solvent” because it can dissolve the most substances than any other liquid. Electrical charge differential helps it dissolve ions, like sodium chloride. Water molecules are attracted to each other - creates surface tension Water forms drops, capillary action allows water to be sucked up plant roots and blood vessels Water is a polar compound. Ions are needed for life! Water can also dissolve uncharged organic compounds, like sugars. It is found in all three states solid, liquid, gas on the Earth

Methane and Ethane Liquids Are hydrocarbons - so have a greasy nature. Are non-polar compounds so they: -don’t dissolve ions. -don’t have much surface tension.

Lecture 34. Extrasolar Planets. reading: Chapter 9