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Clicker Question:

Why is Venus the hottest planet in the Solar System?

A: It is the closest planet to the Sun.

B: There is a lot of radioactive material in the crust.

C: There is a large concentration of carbon dioxide in the atmosphere.

D: The Russians left the lights on in the Venera 5 landing vehicle.

E. Paris Hilton lives there.

Mars

Mass = 0.11 MEarth

Radius = 0.53 REarth

Density = 3.9 g/cm3

Average distance from Sun = 1.52 AU

eccentricity = 0.093

Range in distance from Sun = 1.38 - 1.66 AU

Rotation Period = 24.6 hours

Orbital Period = 687 days

The Martian Atmosphere

- 95% CO2

- Surface Pressure 0.006 that of Earth's atmosphere (thin air!)

- Surface Temperature 250 K.

- Dust storms sometimes envelop most of Mars, can last months.A “Reverse Runaway Greenhouse Effect”? During volcanic phase (first two billion years), thicker atmosphere, warmer surface, possibly oceans. Gradually most CO

2 dissolved into

surface water and combined with rocks, then atmospheric and surface water froze (creating ice caps and probable permafrost layer).

Mars' Moons Phobos and Deimos

Phobos: 28 x 20 km

Deimos: 16 x 10 km

Properties similar to asteroids. They are probably asteroids captured into orbit by Mars' gravity.

Clicker Question:

From Mars, Deimos has an angular diameter of 140 arcseconds. Would colonists on Mars ever see Deimos produce a total solar eclipse?

A: Yes, every day on Mars

B: Yes, every new moon

C: Yes, but rarely

D: Never

The Martian Surface

Valles MarinerisOlympus Mons Tharsis Bulge

Southern Hemisphere ~5 km higher elevation than Northern, and more heavily cratered. South is like lunar highlands, surface ~4 billion years old, North like maria, ~3 billion years old.

Valles Marineris - 4000 km long, up to 7 km deep. Ancient crack in crust. Reasons not clear.

Tharsis Bulge - highest (10 km) and youngest (2-3 billion years) region.

Olympus Mons - shield volcano, highest in Solar System, 3x Everest in height. 100 km across.

(Mars Global Surveyor radar data)

View From the Surface

Viking 1 site (1976) Sojourner robot from Pathfinder (1997)

Dry, desert-like. Red => high iron content. Mars didn't differentiate as completely as Earth. Sky has butterscotch hue due to dust.

Opportunity panorama: inside Victoria Crater

Deepest crater explored by far (230 feet) => apparently it was the top of an underground water table.

Evidence for Past Surface Water

"runoff channels" or dry rivers

"outflow channels"

teardrop "islands" in outflow channels standing water erosion in craters?

South North

Red arrows: rounded boulders indicating water erosion?White arrows: "conglomerate" rock, like in Earth's riverbeds?Blue arrows: sharp-edged boulders, volcanic rock?

Pathfinder site was an outflow channel

Did Mars once have a huge ocean?

Long stretches along border are very even in elevation, like a coastline

Ocean fed by outflow channels fromhigher elevation southern hemisphere?

Evidence for "Permafrost" layer beneath surface

"Splosh" craters suggesting liquefied ejecta.

Evidence for Water on Mars Now

Phoenix Lander (2008) Deployable arm

subsurface ice

Phoenix mission – icy soil at the poles!

Phoenix analyzing scooped updirt – was Mars ever favorablefor microbial life? Organiccompounds?

Mars' History

Smaller than Earth, Mars cooled faster.

Atmosphere and surface water in first 1.5 billion years. Life?

Most volcanic activity ended two billion years ago.

Differentiation less complete than on Earth.

No evidence for plate tectonics.

Atmosphere mostly froze out into subsurface ice, polar icecaps and surface rocks.

Clicker Question:

The largest mountain in our solar system is:

A: Caloris Basin range on Mercury

B: Gula Mons on Venus

C: Mt. Everest on Earth

D: Olympus Mons on Mars

Clicker Question:

Where is the water that once flowed on the surface of Mars?

A: In the atmosphere

B: In the polar caps only

C: In a layer of permafrost below the surface and in the polar caps

D: It was diverted to Los Angeles

Martian ‘Snick’ meteorite ALH84001 shows odd shaped features that are reminiscent of bacteria. General consensus is no life.

Evidence for "Permafrost" layer beneath surface

"Splosh" craters suggesting liquefied ejecta.

Valles Marinaris flyover movie

The Face on MarsViking orbiter photos showed this:

Newer, high resolution photo – Mars Global Surveyor 1998

Isn’t this more disturbing???

Spirit and Opportunity Rovers

Scenes from “Roving Mars” (start at 15:10, skip to 20:27, skip to 26:16)

The Jovian Planets

Jupiter Saturn (from Cassini probe)

Uranus Neptune

(roughly to scale)

Discoveries

Jupiter and Saturn known to ancient astronomers.

Uranus discovered in 1781 by William Herschel.

Neptune discovered in 1845 by Johann Galle. Predicted to exist by John Adams and Urbain Leverrier because of irregularities in Uranus' orbit.

Jupiter

Saturn

Uranus

Neptune

318

95

15

17

Mass (M

Earth)

11

9.5

4

3.9

Radius (R

Earth)

(0.001 MSun

)

Orbit semi-major axis (AU)

Orbital Period (years)

5.2

9.5

19.2

30.1

11.9

29.4

84

164

Major Missions

Voyager 1

Voyager 2

Galileo

Cassini

Launch Planets visited

1977

1979

1989

1997

Jupiter, Saturn

Jupiter, Saturn, Uranus, Neptune

Jupiter

Jupiter, Saturn

Basic Properties

Optical – colors dictated by how molecules reflect sunlight

Infrared - traces heat inatmosphere, therefore depth

So white colors from cooler, higher clouds, brown from warmer, lower clouds. Great Red Spot – highest.

Jupiter's Atmosphere and Bands

Whiteish "zones" and brownish "belts".

Composition: mostly H, some He, traces of other elements (true for all Jovians). Gravity strong enough to retain even light elements. Mostly molecular. Spectroscopy of reflected sunlight reveals which molecules present.

Altitude 0 km defined as top of troposphere (cloud layer)

NH4SH

(NH3)

These molecules should all give white clouds. Molecules responsible for colors actually not clear!

Other Jovian planets: banded structure and colors

More uniform haze layer makes bands less visible. Reason: weaker gravity allows clouds torise higher and spread out to create more uniform layer

Blue/green of Uranus and blue of Neptune due to methane. Colder than Jupiter and Saturn, their ammonia has frozen and sunk lower. Methane still in gas form. It absorbs red light and reflects blue.

- Zones and belts mark a convection cycle. Zones higher up than belts.

-- Zones were thought to be where warm gas rises, belts where cooled gas sinks. Now less clear after Cassini, which found numerous upwelling white clouds in the dark belts.

- Winds flow in opposite directions in zones vs. belts. Differences are hundreds of km/hr.

- Jupiter's rapid rotation stretches them horizontally around the entire planet.

Storms on Jovian Planets

Jupiter's Great Red Spot: A hurricane twice the size of Earth. Has persisted for at least 340 years. Reaches highest altitudes.

New storm “Oval BA”

"white ovals" - may last decades

"brown ovals" - only seen near 20° N latitude. Not known why. May last years or decades

Neptune's Great Dark Spot: Discovered by Voyager 2 in 1989. But had disappeared by 1994 Hubble observations. About Earth-sized.

Why do these storms last so long?

Jupiter's Internal StructureCan't observe directly. No seismic information. Must rely on physical reasoning and connection to observable phenomena.

(acts like a liquid metal, conducts electricity) Core thought to be molten or partially molten rock,

maybe 25 g/cm3, and of mass about 10-15 MEarth

.

Other Jovians similar. Interior temperatures, pressures and densities less extreme.

Rapid rotation causes Jupiter and Saturn to bulge:

Gravity

without rotation with rotation

Gravity

Jupiter and Saturn rotate every ~10 hours. Radius at equator several % larger due to bulge.

Differential Rotation

Rotation period is shorter closer to the equator:

Jupiter

Saturn

Uranus

Near poles At equator

9h 56m

10h 40m

16h 30m

9h 50m

10h 14m

14h 12m

How do we know?

Differential Rotation

Rotation period is shorter closer to the equator:

Jupiter

Saturn

Uranus

Near poles At equator

9h 56m

10h 40m

16h 30m

9h 50m

10h 14m

14h 12m

How do we know? Tracking storms at various latitudes, or using Spectroscopy and Doppler shift.

Uranus' rotation axis is tilted by 98o

Why? Unknown. Perhaps an early, grazing collision with another large body.