Venus “lite” Currently in southwest sky after sunset, ( greatest elongation of 47 degrees was...
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Transcript of Venus “lite” Currently in southwest sky after sunset, ( greatest elongation of 47 degrees was...
Venus “lite”Venus “lite”
Currently in southwest sky after sunset,
( greatest elongation of 47 degrees was Nov 3rd ), magnitude -4.3
Stays low, reaches inferior conjunction January 13, 2006
Magellan radar of Maat MonsMagellan radar of Maat Mons
Rises 8km
High due to no plate motion (one continental plate)
Planet resurfaced about 500M years ago
A Morning/Evening “star”A Morning/Evening “star”
Limited by maximum elongation …Limited by maximum elongation …
.. Of 29.. Of 29OO, maximum, maximum
Mercury (also) reached greatest elongation east (24 degrees) on Nov 3rd Still in SSW, magnitude about -0.1
..
AlbedosAlbedos
Mercury bright in spite of low Mercury bright in spite of low albedoalbedo Albedo = percent of light reflectedAlbedo = percent of light reflected Mercury dark, albedo ~ 11% (7% for the Moon)Mercury dark, albedo ~ 11% (7% for the Moon) Clouded planets high, 72% for Venus, half that for Clouded planets high, 72% for Venus, half that for
the Earththe Earth
TransitsTransits Crossing Crossing
between us and between us and the Sun is a the Sun is a “transit”“transit”
Venus and Venus and Mercury both Mercury both do itdo it
This from the This from the TRACETRACE
Venus transited Venus transited June 8, 2004June 8, 2004
Spin-orbit resonanceSpin-orbit resonance Orbit takes Orbit takes
88 days88 days Rotation is Rotation is
2/3 of this 2/3 of this (~59 days)(~59 days)
3:2 spin-orbit 3:2 spin-orbit resonance, resonance, due to tidal due to tidal forces at forces at perihelionperihelion
Combined, Combined, the Mercury the Mercury “day+night” “day+night” is 176 days is 176 days longlong
Mariner 10 compositeMariner 10 composite
Heavily crateredHeavily crateredEjecta not thrown Ejecta not thrown
as far as on Moonas far as on Moon
ScarpsScarps
Cliffs that Cliffs that form along form along faultsfaults
Not tectonic Not tectonic like on Earthlike on Earth
Probably Probably wrinkles due wrinkles due to impactsto impacts
Caloris BasinCaloris Basin
Large circular Large circular region of impact region of impact (left side of this (left side of this image)image)
If look at opposite If look at opposite hemisphere…hemisphere…
Magnetic fieldMagnetic field
Magnetic field ~ 0.5 % Earth’s, suggests…Magnetic field ~ 0.5 % Earth’s, suggests…
Interior structureInterior structure
Must have a large metal core to get high density Must have a large metal core to get high density without the Earth’s larger gravity to compresswithout the Earth’s larger gravity to compress
Large fraction of iron suggests impact origin …Large fraction of iron suggests impact origin …
… … like thislike this
Impact throws of most silicates, leaving large fraction of ironImpact throws of most silicates, leaving large fraction of iron
Future MissionsFuture Missions NASA has the NASA has the
MessengerMessenger mission under mission under way, launched way, launched August, 2004 , will August, 2004 , will make several make several flybys of Earth & flybys of Earth & Venus before Venus before orbits Mercury in orbits Mercury in March of 2011March of 2011
ESA/Japan have ESA/Japan have BepiColomboBepiColombo “in “in development”development”