a1 08 venus mars geo

Geology of VenusLACC §9.1, 9.2, 9.4

• Know Venus’s interior and evolution

• Know Venus’s surface features and age

• Understand Venus’s day

An attempt to answer the “big question”: what is out there? Are we alone?

1Tuesday, March 9, 2010

Terrestrial Planets: Interiors

http://www.star.le.ac.uk/edu/Solar_System.shtml

(which amounts to 30.1 Earth diameters)http://hyperphysics.phy-astr.gsu.edu/hbase/solar/moonscale.html#c2

Earth and Moon to Scale




http://hyperphysics.phy-astr.gsu.edu/hbase/solar/moonscale.html#c2

http://hyperphysics.phy-astr.gsu.edu/hbase/solar/moonscale.html#c2

Terrestrial Planets: Orbits

http://www.schoolsobservatory.org.uk/astro/solsys/inner.shtml

The size of the orbits of each planet are to scale, although the size of the planets themselves are much too large.




Terrestrial Planets: Surface Gravity

http://www.exploratorium.edu/ronh/weight/

If you weigh 100 pounds on Earth...

(These worlds are not to scale.)




Terrestrial Planets: The Sun in the Sky

The sun is about 0.5° across as it appears from Eath

(These worlds are not to scale.)

* But you can’t see the sun through the clouds

1.4°6.7x brighter

0.7°1.9x brighter*

0.5°1.0x brighter

0.35°0.4x brighter


Venus

http://www.astrosurf.com/nunes/explor/explor_m10.htm




Venus: Surface Features

Impact craters indicate a surface age of 500 million years (15% as old as lunar maria and between the age of Earth’s younger ocean sea-floor and older continents); yet erosion rates are very low.

Volcanoes on Venus are about as common as on Earth, but Venus has “pancake” volcanoes in addition to shield, volcanoes. Coronae (circular bulges) are more common on Venus.

Tectonic activity does occur on Venus: ridges, cracks, mountains, the coronae; but no plate tectonics.


Venus: Pancakes & Crater

http://photojournal.jpl.nasa.gov/jpegMod/PIA00084_modest.jpg




Venus: Corona

http://photojournal.jpl.nasa.gov/jpeg/PIA00202.jpg




Venus: Oddities

Venus rotates backwards and slowly. A solar day on Venus is 117 days, and the sun rises in the west and sets in the east, not that you would ever see the sun through the dense clouds.

Venus’s slow rotation (sidereal day: 243 days (longer than its year: 225 days!)) results in low wind velocities and low erosion rates on the surface.


Geology of VenusLACC §9.1, 9.2, 9.4

• Know Venus’s interior (volcanically inactive?) and evolution (resurfaced about 0.5 billion years ago)

• Know Venus’s surface features (coronae, pancake lave domes, impact craters) and age (0.5 billion years)

• Understand Venus’s day (orbits backwards--CW when most planets are CCW, solar day is 117 days (its sidereal day: 243 days, is longer than its year: 225 days)



LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe, 3rd ed.

• Ch. 9, pp. 219-220: 10.

Due at the beginning of the next class period.

Be thinking about the Solar System Project.


Geology of MarsLACC §9.1, 9.2, 9.4

• Know Mars’s interior and evolution

• Know Mars’s surface features and age

• Know Phobos and Deimos, Mars’s moons



Mars

http://rosetta.jpl.nasa.gov/dsp_images.cfm?buttonSel=gallery&buttonSelL2=images&category=mars




Mars: Surface FeaturesImpact craters indicate a surface age of 3 - 4 billion years (same as lunar maria) for the Martian lowlands.

Olympus Mons, the largest volcano in the solar system, maybe be intermittently active.

Tectonic activity does occur, but not as much evidence for it as Earth or Venus.

Polar caps of H2O and CO2 ice.

Channels and gullies indicate liquid water flowed, but over 3 billion years ago.

Wind erosion occurs.


Mars: Tharsis Bulge

http://www.britannica.com/eb/art/print?id=70956




Mars: Olympus Mons

http://www.nasm.edu/ceps/etp/mars/surface/canyons.html




Mars: Oddities

In a way, Mars is so much like the Earth, it’s odd:

• Mars’s day is only 42 min. longer than Earth’s

• Mars’s axial tilt is 25°; Earths is 23.5°.

• Mars’s diameter is about 0.53 Earth diameters, which means Mars’s total surface area is about the same as Earth’s land surface area.

Mars has two moons: Phobos and Deimos.

Mars had liquid water at some point in its past, and may have had life.


http://astro.unl.edu/classaction/terrplanets.html



















Mars: Phobos and Deimos

http://apod.nasa.gov/apod/ap061203.html

• 28 x 23 x 20 km

• 7h 39m 27s synod.

• 5h 36m West to East

• 12 x 10 x 6 km

• 30h 21m 16s synod.

• 66h East to West







Mars: Phobos and Deimos• Average Distance from Mars: 9,378 km (Phobos),

23,459 km (Deimos)

• Orbital Period: 7h 39m (Phobos), 30h 18m (Deimos)

• Eccentricity of Orbit: 0.015 (Phobos), 0.0005 (Deimos)

• Rotation Period:7h 39m (Phobos), 30h 18m (Deimos), i.e. both moons are tide locked to Mars

• Density: 2 gm/cm3 (Phobos), 1.7 gm/cm3 (Deimos)

• Atmosphere:n/a

• Surface Temperature: 25°F Max, -170°F Min (Phobos)

http://www.solarspace.co.uk/Mars/phobosdeimos.php




Mars: “Months”Since Mars rotates a bit faster than the revolution period of Deimos, we would indeed see it rise in the east, but it would then appear to move across the Martian sky at a very slow pace. In fact, it would take about 33 hours to reach that point directly overhead (or very nearly so). It would then take yet another 33 hours to descend the sky before we would see it finally set in the west.

And then, we would have to wait another 66 hours before it again reappears above the eastern horizon.

In contrast, Phobos, takes only 7 hours and 39 minutes to rotate around Mars. So it has the distinction of being the only natural satellite in the solar system revolving about its planet in a time shorter than the planetary "day," running three laps around Mars each day.

As seen from the Martian equator, Phobos appears to move far more rapidly than the sluggish Deimos. In fact, just 2 hours and 48 minutes after Phobos has risen, it is already overhead. And after another 2 hours and 48 minutes it is setting; an astronaut on Mars could witness it rising twice during a single Martian night.

And since Phobos west-to-east motion is much faster than Mars rotation period, it would appear to rise in the west and set in the east.

Furthermore, about every 10 hours and 18 minutes, Phobos appears to rapidly race closely past Deimos as they trek in opposite directions. Phobos, in fact, probably even appears to briefly eclipse Deimos for some parts of Mars on each pass.

Try picturing this: during the 66-hours that Deimos moves ponderously in the sky toward the west, Phobos appears to whiz rapidly in the opposite direction more than six times!

http://www.space.com/spacewatch/mars_moons_040116.html




Mars: Moon Phases

Phobos goes through its entire cycle of phases in the short time it takes to go once around Mars.

If, for example, it were rising in the west just as the Sun were setting, it would be at its "New" phase. A little over four hours later, it will already have moved well past the overhead point to a position roughly halfway up in the east and would appear "Full." When it sets in the east about an hour and half later, it will have waned to its Last Quarter phase.

As for Deimos, because the Sun appears to move across the sky more than twice as fast, this moon would appear to go through a full set of phases more than twice during the 66 hours that it is continuously above the horizon.

Unfortunately, because of the very small size of both satellites, we should not expect to see the same kind of sight that we're accustomed to seeing with our own Moon. Deimos, for example, would appear only about 1/19 the apparent width of our Moon. It would shine at its very best when at its "Full" phase, but because of its very small size it would probably look more like an oversized version of Venus to the unaided eye.






http://www.nasaimages.org/luna/servlet/detail/nasaNAS~4~4~11828~113853:The-Night-Sky-on-Mars





http://www.johnstonsarchive.net/astro/phobos.html

Apparent size of the Moon as seen from Earth: 0.5°Apparent size of the Phobos as seen from Mars: 0.18°

Apparent size of Sun as seen from Earth: 0.5°Apparent size of Sun as seen from Mars: 0.35°

Apparent size of Earth as seen from the moon: 1.9°Apparent size of Mars as seen from Phobos: 42°




Mars: Terraformed Mars from Phobos

http://www.users.globalnet.co.uk/~mfogg/gallery.htm

Book cover by Hardy for Carl Sagan's 'Pale Blue Dot'. We see Mars at an advanced stage of terraforming with the Tharsis volcanoes, a flooded Mariner Valley and the Boreal Ocean.




Geology of MarsLACC §9.1, 9.2, 9.4

• Know Mars’s interior (volcanically inactive?) and evolution (some meteorites came from Mars, water once flowed on surface)

• Know Mars’s surface features (poles of H2O and CO2 ice, Valles Marineris, Tharsis Bulge, Olympus Mons--largest volcano) and age (3 to 4 billion years)

• Know Phobos (larger, orbits in less than a day) and Deimos (small, takes 66 hours to cross the sky), Mars’s moons (captured asteroids)



LACC HW: Franknoi, Morrison, and Wolff, Voyages Through the Universe, 3rd ed.

• Ch. 9, pp. 219-220: 15.

• Ch 9: Tutorial Quiz accessible from: http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M20b&product_isbn_issn=9780495017899&discipline_number=19Must Know: 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18Important: 1, 12, 19, 20

Due at the beginning of the next class period.

Be thinking about the Solar System Project.


http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M20b&product_isbn_issn=9780495017899&discipline_number=19






a1 08 venus mars geo

Education

mars http

surface age

phobos http

marss surface features

mars density

monthssince mars

marss day

surface gravityif