Transcript Linking Asteroids and Meteorites through Reflectance

Astronomy 101
The Solar System
Tuesday, Thursday
2:30-3:45 pm
Hasbrouck 20
Tom Burbine
[email protected]
Course
• Course Website:
– http://blogs.umass.edu/astron101-tburbine/
• Textbook:
– Pathways to Astronomy (2nd Edition) by Stephen Schneider
and Thomas Arny.
• You also will need a calculator.
Office Hours
• Mine
• Tuesday, Thursday - 1:15-2:15pm
• Lederle Graduate Research Tower C 632
• Neil
• Tuesday, Thursday - 11 am-noon
• Lederle Graduate Research Tower B 619-O
Homework
• We will use Spark
• https://spark.oit.umass.edu/webct/logonDisplay.d
owebct
• Homework will be due approximately twice a
week
Astronomy Information
• Astronomy Help Desk
• Mon-Thurs 7-9pm
• Hasbrouck 205
•
The Observatory should be open on clear Thursdays
• Students should check the observatory website at:
http://www.astro.umass.edu/~orchardhill for updated
information
• There's a map to the observatory on the website.
Final
• Monday - 12/14
• 4:00 pm
• Hasbrouck 20
HW #15
• Due next Tuesday
Exam #3
• This Thursday
• Covers material from October 15th – November 5th
• Bring pencil and a calculator
• Review Session – Wed. at 6 pm in Hasbrouck 134
• Formulas (I also would not forget the formulas that I
learned earlier)
Density = mass/volume
Volume = 4/3r3
HW Review
Mercury/Venus
• Mercury is the closest planet to the Sun
• Venus is next closest
Mercury
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orbit: 0.38 AU from Sun
diameter: 4,880 km (38.3% of Earth)
mass: 3.30 x 1023 kg (5.5% of Earth)
temperature:
90 K (minimum)
440 K (average)
700 K (maximum)
• Satellites: Zero
Difficult to study Mercury
• Because of Mercury's proximity to the Sun
– makes reaching it with spacecraft technically
challenging
– Earth-based observations difficult.
Mercury
• Videos
• http://www.gecdsb.on.ca/d&g/astro/html/Mercury
.html
Mariner 10
• The only spacecraft to approach Mercury was
NASA's Mariner 10 (1974-1975).
Caloris Basin
Caloris Basin
(Some of the hill are 1,800 meters tall)
Messenger data
Mariner 10 data
Caloris Basin
• A basin was defined by Hartmann and Kuiper (1962) as a
"large circular depression with distinctive concentric
rings and radial lineaments."
• Others consider any crater larger than 200 kilometers a
basin.
• The Caloris basin is 1,550 kilometers in diameter, and
was probably caused by a projectile larger than 100
kilometers in size.
• The impact produced concentric mountain rings three
kilometers high and sent ejecta 600 to 800 kilometers
across the planet.
Weird Terrain
The weird terrain is almost opposite
Caloris Basin. It consists of hills,
ridges and grooves that cut across craters.
The weird terrain my have been formed by
shock waves that raced through the center
of the planet and outward early in
Mercury's history.
Mercury has high density
• Its density is 5.44 g/cm3 which is comparable to
Earth's 5.52g/cm3 density.
• In an uncompressed state, Mercury's density is 5.5
g/cm3 where Earth's is only 4.0 g/cm3.
http://www.psrd.hawaii.edu/WebImg/MercuryCore.gif
Messenger
• Mission to Mercury
• Launched August 3, 2004
• Flew by Mercury in 2008
and 2009
• Will orbit Mercury in
2011
Messenger video
• A set of five 11-band images was captured by MESSENGER
just after the spacecraft crossed the night/day line (the
“terminator”), which are the highest-resolution color images
ever obtained of Mercury’s surface.
• At the beginning of this movie, it is dawn in that region of
Mercury, and the Sun is just off the horizon. The long
shadows that are cast by crater walls exaggerate the
ruggedness of the terrain and highlight variations in
topography.
• Though Mercury’s true colors are subtle, the 11 color bands
of MDIS were combined in a statistical method used to
highlight differences in color units. Older, low-reflectance,
and relatively blue material is encroached by younger,
relatively red smooth plains. Several lobate scarps or cliffs
are observed, which are places where compressional stresses
caused Mercury’s crust to fracture and shorten.
http://messenger.jhuapl.edu/news_room/presscon5_images/Robinson%20Image%205.7.mov
Mercury
Much of the image to the right of the Kuiper crater (in the centre here)
had never been imaged by a spacecraft before. Researchers were
surprised to see long crater rays that extend thousands of kilometers from
a crater at the planet's north pole
http://space.newscientist.com/data/images/ns/cms/dn14893/dn14893-1_450.jpg
Mercury
Dark material, shown in deep blue in the enhanced colour image at
right (a composite of visible and near-infrared images), was kicked up
by impacts. The material seems to be widespread but patchy,
suggesting the planet's interior is not homogenous.
http://space.newscientist.com/data/images/ns/cms/dn15077/dn15077-1_600.jpg
Mercury
• Double ringed basin
• 290 km in diameter
• Appears young (few
craters on it)
• ~ 1 billion years old
• Lava may have
covered up the central
part of the basin
http://messenger.jhuapl.edu/gallery/sciencePhotos/pics/presscon6_img4_5_lg.jpg
• 160 km in diameter
http://en.wikipedia.org/wiki/File:Mercury_Double-Ring_Impact_Basin.png
Spectra of Mercury
Weak to absent absorption features – no iron in the silicates
Mercury’s Surface
• Made of Enstatite (MgSiO3) – Mg-rich pyroxene
• Made of material like the Lunar Highlands
– Plagioclase feldspar - CaAl2Si2O8
Venus
• orbit: 0.72 AU from Sun
• diameter: 12,103.6 km (94.9% of Earth)
(called Earth‘s twin)
• mass: 4.869 x 1024 kg (81.5% of Earth)
• Temperature on surface:
726 K(average)
• Satellites: Zero
Venus’ atmosphere
• Atmospheric pressure at surface is 92 times the
pressure on the Earth’s surface
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Atmospheric content:
Carbon dioxide
96.5 %
Nitrogen
3.5 %
Sulfur dioxide
150 ppm
Argon
70 ppm
Water vapor
20 ppm
Venus’ clouds
• Venusian clouds are thick and are composed of
sulfur dioxide and droplets of sulfuric acid.
• These clouds reflect about 75% of the sunlight
that falls on them,
Greenhouse Effect
• The greenhouse effect is the rise in temperature
that a planet experiences because certain gases in
the atmosphere (H2O, CO2, CH4) trap energy
emitted from the surface.
• Visble light hits the surface
• Surface warms and emits infrared radiation
• Atmospheric gases absorb some of the infrared
light
• Surface and Atmosphere heat up
Stefan-Boltzman Law
Emitted power (per square meter of surface) = σT4
λ·Tmax = 2,900,00 nm
Runaway Greenhouse Effect
• Runaway greenhouse effect to describe the effect
as it occurs on Venus
• Venus is sufficiently strongly heated by the Sun
that water is vaporized and so carbon dioxide is
not reabsorbed by the planetary crust
Why does Venus has such
a thick atmosphere?
• The luminosity of the Sun has increased by 25%
from 3.8 billion years ago
• The atmosphere of Venus up to around 4 billion
years ago maybe was more like that of Earth with
liquid water on the surface.
• The runaway greenhouse effect may have been
caused by the evaporation of the surface water
and the rise of the levels of greenhouse gases that
followed.
Surface
• Mapped by Magellan
spacecraft (1990-1994)
• How was it mapped if it
has a dense atmosphere?
How did it do it?
• Used Radar (radio waves)
• Most of Venus' surface consists of gently rolling
plains with little relief.
• Data from Magellan's imaging radar shows that
much of the surface of Venus is covered by lava
flows.
• Lava flows stopped ~300-500 million years ago
• Very few craters
Craters
• Venusian craters range from 3 km to 280 km in
diameter.
• There are no craters smaller than 3 km because
the dense atmosphere stops small incoming
objects.
• 200 km long channel
• 2 km wide
http://hyperphysics.phy-astr.gsu.edu/hbase/Solar/venusurf.html
Pancakes Domes
• Flattened lava domes are attributed to upwellings
of molten rock which then subsided.
• The solid crust left behind
then flattened and cracked.
Coronae
• Corona is an oval-shaped feature.
• hot rising bodies of magma reach the crust and
cause it to partially melt and collapse
• Generates volcanic flows and fault
patterns that radiate from the
central structure.
100 km in diameter
http://pds.jpl.nasa.gov/planets/captions/venus/vencor.htm
Arachnoids
• concentric ovals surrounded by a complex network of
fractures, and can span 200 kilometers
• Almost all Venusian surface features are named
after historical and mythological women.
• The only exceptions are Maxwell Montes, named
after James Clerk Maxwell, and two highland
regions, Alpha Regio and Beta Regio
Venera
• Venera probes were launched by the Soviet Union
and enter Venus’ atmosphere
• 1961-1984
• Venera 3-16
• 10 probes landed on surface
Venera 9
Venera 9 pictures
Venus Express
• Launched November 9, 2005 (Soyuz-Fregat from
Baikonur, Kazakhstan)
• First global monitoring of composition of lower
atmosphere in near-infrared transparency ‘windows’
• First coherent study of atmospheric temperature and
dynamics at different levels of atmosphere, from surface
up to ~200 km
• First measurements from orbit of global surface
temperature distribution
Mostly spare parts from
Mars Express or Rosetta
• ASPERA-4 - Neutral and ionised plasma analysis - Mars
Express
• MAG - Magnetic field measurements - Rosetta Lander
• PFS - Atmospheric vertical sounding by infrared Fourier
spectroscopy - Mars Express
• SPICAV - Atmospheric spectrometry by star or Sun
occultation - Mars Express
• VeRa - Radio sounding of atmosphereFrance)VeRaRadio
sounding of atmosphere - Rosetta
• VIRTIS - Spectrographic mapping of atmosphere and surface
- Rosetta
• VMC - Ultraviolet and visible imaging Mars Express and
Rosetta
Any Questions?