Lecture 33. Cassini-Huygens Mission.

reading: Chapter 8

Saturn

Pioneer 11 flyby in 1979V1 in 1980 and V2 in 1981.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-gainantennae to Earth, picked up by the DeepSpace Network, sending Gigabytes of datadaily.

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Orbiter Instruments

Wide angle and narrow angle camera10 Megapixel CCD sees a quarter 4 km away.

Cosmic Dust Analyzercounts dust grainsIon and Natural Mass Spectrometerstudies positive ions and neutral particles in upper atm. of Titan and

magnetosphere of SaturnMagnetospheric Imaging Instrumentfirst instrument to produce an image of a magnetosphere and

ionized gases (plasma)MagnetometerRadio and Plasma Wave Science Instrumentmeasures radio signals from Saturn, from interaction of solar wind with

Saturn and TitanRADARuses microwaves to image TitanRadiowhat is this used for??

Spectrometer splits light into its component wavelengths,fingerprint of compounds present.

Mapping component makes a map of where thedifferent 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 surfaceParts have no craters >35 kmOthers have no cratersFissuresPlainsCorrugated terrainCrustal deformations

Interior may be liquidDon’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, CH4, 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 1655.Built and designed by ESA.On Dec. 2004 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 Instrumentmeasures physical properties of the atm, density, wind gusts, waves (if

probe landed in an ocean), conductivity of surface

Doppler Wind Experimentwind speed during descent

Descent Imager/Spectral RadiometerMeasures upward and downward flow of light

Aerosol Collector and Pyrolyser and GCMSheated aerosols and sent to GCMS, GCMS measured composition of atm.

Surface Science Packageseveral 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. Waterice 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:C6H6, C2N2, CO2

Suggests complex chemistry occurring on the surface, and differentfrom the atm.

Surface wet with methane.

Penetrometer:surface consistency of loose wet sand

Huygens - Atmosphere

Landing site: 93.7K, 1.47 barsWinds at 120 km were 450 kphWinds at 100-60 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 compoundsfound in the atmosphere.

May be unidentified organic compounds on the surface.

40Ar 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 itcan dissolve the most substances than anyother 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 upplant roots and blood vessels

Water is a polar compound.Ions are needed for life!

Water can also dissolveuncharged organiccompounds, like sugars.

It is found in all three statessolid, 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

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