Magnetic and How Lost Its

Bob Lin Physics Department & Space Sciences Laboratory Universityyf of Calif ornia, Berkeley

Also (visiting) School of Space Research Kyung Hee University, Korea

Thanks to the MGS, MAVEN, and LP teams ’s

The Earth’s Explorer 35 (1967)

Lunar Shadowing Apollo 15 Mission -1971

Lunar Rover ->

<- Jim Arnold's Gamma-ray Spectrometer

<- Apollo 15 Subsatellite ->

<= SIM (Scientific Instrument Module) Lunar Shadowing

<= Downward electrons

<= Upward electrons

<= Ratio of Upward to DdltDownward electrons

Electron Reflection Trajectory Converging Magnetic Fields

Secondary Electron

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dv||RemotelydU SensingdB Surface MagneticB Fields by m + e + μ = 0⇒sin 2 α = LP []1- eΔU E Planetary Electron Reflection Magnetometryc (PERM) dt ds ds BSurf Apollo 15 & 16 Electron Reflectometry

OneHowever, of the the great Apollo surprises 15 & 16 from Apollo was magnetic the discovery data set of paleomagneticis very sparse and fields confined in the lunar within crust 35 degrees. Their existence of the suggestsequator. Attempts that magnetic to correlate fields atsurface the magnetic were muchfields with strongerspecific geologic in the past features than they were are largely today. unsuccessful.

Mars Observer (1992-3) – disappeared 3 days before Mars insertion Mars Global Surveyy(or (MGS ) 1996-2006 MGS Mag/ER team Current state of knowledge • Very strong crustal fields measured from orbit: – Discovered by MGS: ~10 times stronger than terrestrial fields. – Reqirehgeolmes(>10Require huge volumes (>106 km3) of coherentl y magneti zed cr ust . – Crustal remnant of a strong dynamo-driven global magnetic field MGS Mars Magnetic Map (from Electron Reflection) What do we Learn about Mars?

No significant global field Interior incapable of supporting dynamo today

Strong localized magnetic fields Oldest crust magnetized in ancient dynamo Impacts/volcanism erased many sources

Variable solar field create randomness in map Atmosphere exposed to in many regions Current state of knowledge • Distribution of crustal fields: – Follows the dichotomy to first-order: strong in South, weak in North. – Shock demagnetization by post-dynamo impacts – Thermal demagnetization by magmatic intrusions (e.g. Tharsis) Current state of knowledge • The Martian dynamo: – Rapid cessation in basin magnetization around 4.1 Gyr ago (H&N).

– EittiExcitation mech hianisms: i iitilhtnitial hot core, i nner core f ormati tiion, impact – Termination mechanisms: cooling core, giant impact – Lack of global field → increased atmospheric loss. – Withi n 0 -300 Myr o f cessat , c limate h ad lik y b ecome much d ri er ( end of the Phyllosian era). Martian Climate Evolution

Many lines of evidence point to a change in the Martian atmosphere from Earth-like to cold and thin Where did the Atmosphere Go?

Up UP

Down Pickup

Aurora in the

Jupiter Observations of Auroral Processes

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Brain et al., 2006 Lundin et al., 2006

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QuickTime™ and a decompressor are needed to see this picture. (Earth) Consequences of ?

(Earth)

ESAESA

MGS Atmospheric Probing Results Atmosph eri c neut ral d ensit y f rom MGS ER measurements, at of 0-30 S (diamonds), 50-55 S (triangles) and all latitudes (solid line). Dashed lines show aphelion and perihelion.

Atmospheric

Solar Energetic Particles Effects on Atmosphere

• Solar Energetic Particle (SEP) events: – detectable in MGS ER background – deposit energy in atmosphere, heating atmospheric neutrals Protons – enhance atmospheric –contibttribute t o M ars’ radi ditiation envi ronment Electrons

COUP: The Movie (courtesy Feigelson, 2007) Extraordinary flares in analoggygs of the young

1 2 JW 738

K=10.5 ts / ks cc Age ~ 10 Myr

log Lp = 32.6 erg/s X-ray

Time (13.2 days) Flare 1: Unusual slow-rise morphology.

Flare 2: One of the most powerful X-ray flares ever seen 36.8 in any late-type star with Ex ~ 10 erg.

Wolk & 7 others 2005 COUP #6 Mars Atmosphere and Volatile EvolutioN (MAVEN) Mars Scout Mission

Bruce Jakosky, Principal Investigator University of Colorado Bob Lin, Deputy PI Univ. of California, Berkeley

MAVEN Team