Download Aim of this course: Course Outline

Aim of this course:
The Terrestrial Planets
Lecture 1: Introduction
Provide a general introduction to the four terrestrial
(Earth-like) planets (Mercury, Venus, Earth and Mars).
By the end you should be able to identify their major
features and their common or unique properties.
?
The Terrestrial planets at correct relative size:
Mercury
Course Outline
Lecture 1
Lecture 2
Lecture 3
Lecture 4
Lecture 5
Lecture 6
Lecture 7
Lecture 8
Introduction
Earth – interior
Earth – atmosphere
Venus – Earth’s twin?
Mars – dead or alive?
Mercury – dense and hot
The Moon – properties & origin
Summary & Planet Formation
Venus
Earth
Mars
Course books, handouts and the WWW
Listed textbook for this course:
“Discovering the Solar System” by Barrie W. Jones
Good for detail and if doing several planet courses
Any modern introductory astronomy text – e.g.
“Astronomy Today” by Chaisson & McMillan
On-line: brief summary handout (as given out today) and
(incomplete – images and tables) copies of each lecture, at
http://www.star.le.ac.uk/pto2/planets.html
You need to take notes of text material during lectures
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MANY web pages – some recommended examples:
http://nineplanets.org
A multimedia tour of the Solar System.
http://www.solarviews.com/eng/
Another multimedia experience.
Quiz: name the 10 largest objects in
the Solar System (excluding the Sun)
Jupiter
Saturn
71490 km
60270 km
Uranus
25560 km
Neptune
24765 km
Earth
6378 km
http://exoplanet.eu
An excellent site for information on extra-solar planets.
Venus
6052 km
http://www.nasm.si.edu/apollo/
Site for information on the Apollo missions to The Moon.
Mars
Ganymede
3397 km
2635 km (Moon of Jupiter)
Titan
Mercury
2575 km (Moon of Saturn)
2440 km
Introducing the Solar System
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What is in the Solar System?
Sun, planets, moons, asteroids, comets, dust…
The Planets
• The planets orbit counterclockwise in the Ecliptic plane
• Orbits are ellipses, with Sun at one focus – most with small
eccentricity (e) (orbits obey Kepler’s Laws)
• Earth orbits Sun at mean distance of one “Astronomical Unit”
Sun = 99.85% of mass
Comet West
Eros
• Mercury’s orbit (and Pluto) has a significant eccentricity and
inclination (angle from Ecliptic plane)
Dust
?
Planets = 0.135% of mass!
Planetary data
Asteroids – interplanetary debris
• Over 100,000 known - most between Mars and
Jupiter (>100m are asteroids; rest are meteroids)
Planet
Orbital
semi-major
axis (AU)
Orbital
Period
(years)
Mass
(Earths)
Diameter
(Earths)
Average Density
(kg/m³)
Mercury
0.387
0.241
0.055
0.383
5430
• Total mass < 0.05 x Moon. Largest is Ceres (940 km)
Venus
0.723
0.615
0.815
0.949
5240
• Earth-crossing
Earth
1.000
1.000
1.000
1.000
5520
• Source
Mars
1.524
1.881
0.107
0.533
3940
Jupiter
5.203
11.86
317.83
11.21
1330
Saturn
9.555
29.42
95.16
9.45
700
Uranus
19.22
83.75
14.50
4.01
1300
Neptune
30.11
163.7
17.20
3.88
1760
Pluto
39.54
248.0
0.0025
0.180
2100
asteroids are of great interest!
of most meterorites/meteors
Iron & Nickel –
rare, similar to
type M asteroids
Chondrite –
similar to
terrestial
mantle/crust
3
NASA Near Earth Asteroid Rendezvous Mission
NASA Stardust Mission
Principal target: asteroid Eros
Arrived late 1998; landed Feb. 12 2001
Target: Comet Wild 2
Landing image:
Distance 250 m
Image = size of
lecture room
View from 500 km – looks like an asteroid surface
East and West hemispheres
Size 33 x 13 x 13 km
Big craters, grooves, then smaller
craters – get evolutionary sequence
from surface features
The Kuiper Belt and Pluto (&TNOs)
Left image: short exposure - see craters, boulders etc.
Right image: long exposure - see dust jets
Pluto
~1010
Kuiper belt:
icy objects beyond Neptune (30–1000 AU)
Pluto is a large example.
Quaoar discovered in 2002 – half the size of Pluto. Other
large objects found since (e.g. Sedna; 2003 UB313 (Eris)).
See changes in colour over time and in mass of atmosphere.
May be due to melting/warming of nitrogen ice.
4
Is Pluto a planet?
Question: Should other large objects at similar distances to
Pluto (including Pluto) also be called planets?
All are in inclined, eccentric orbits
with periods of 300-600 years.
Several have moons.
Eris and Dysnomia
Eris is the Greek goddess of strife and discord. Her
child, Dysnomia, is the goddess of Lawlessness.
Dysnomia’s orbit allows for an accurate mass estimate: M(Eris) = 1.27 x M(Pluto)
Where is Eris?
IAU resolutions 2006
(or, how to lose friends and influence nobody)
Eris density (~2.5 kg m-3) similar to Pluto (~1.8 kg m-3) (low compared to Earth)
IAU resolutions 2006
(or, how to lose friends and influence nobody)
5A. The IAU therefore resolves that "planets" and other bodies in our Solar System, except
satellites, be defined into three distinct categories in the following way:
5A. The IAU therefore resolves that "planets" and other bodies in our Solar System, except
satellites, be defined into three distinct categories in the following way:
(1) A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its
self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly
round) shape, and (c) has cleared the neighbourhood around its orbit.
(1) A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its
self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly
round) shape, and (c) has cleared the neighbourhood around its orbit.
(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass
for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium
(nearly round) shape , (c) has not cleared the neighbourhood around its orbit, and (d) is not a
satellite.
(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass
for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium
(nearly round) shape , (c) has not cleared the neighbourhood around its orbit, and (d) is not a
satellite.
(3) All other objects except satellites orbiting the Sun shall be referred to collectively as "Small
Solar-System Bodies".
(3) All other objects except satellites orbiting the Sun shall be referred to collectively as "Small
Solar-System Bodies".
6A. The IAU further resolves:
6A. The IAU further resolves:
Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new
category of trans-Neptunian objects.
Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new
category of trans-Neptunian objects.
5
The Oort cloud
Extends to 100,000 AU with total mass = 30 x Earth
4th October 1957
Sputnik 1 launched
27th August 1962
Mariner 2 - the first
interplanetary craft flies to Venus
6
20th July 1969
Apollo 11 lands on Moon
29th March 1974
Mariner 10 reaches Mercury
Messenger flyby 1,2,3:
Feb. 14 & Oct. 6 2008, Sept. 29 2009
July 1976
Viking landers touch down on Mars
20th August 1977
Voyager 2 launched
5th September 1977 Voyager 1 launched
No Martians seen…
Followed Pioneer missions (launched 1972/73) to Jupiter
7
Voyager mission used “Gravitational slingshot”
1981 Voyager 2 image of Saturn. Voyager finds 3
new moons and complex structure in the rings
July 1979
Voyagers discover Volcanism on Io and
3 new moons of Jupiter
January 1986 Voyager 2 reaches Uranus.
Finds 10 moons and measures a magnetic field
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August 1989 Voyager 2 passes Neptune, finding 6
moons and geysers on Triton
1990-1994 Magellan maps Venus
Feb 14 1990 Voyager 1 portrait of the Solar System
September 1992
First Kuiper Belt Object discovered
9
1995
First extra-solar planet discovered by
Michel Mayor and Didier Queloz
15th October 1997
Cassini-Huygens mission to
Saturn launched – arrived July 2004
December 7th 1995
Galileo drops probe into Jupiter
Probe entered atmosphere at 106,000 mph (x100 rifle bullet)
January 2004
ESA Mars Express image of Gusev crater +
image from NASA Spirit rover
Saturn and Titan from 285 million km
10
Cassini (Saturn)
& Huygens probe (2005, Titan)
Deep Impact – Comet Tempel 1: 2005 July 4
Surface image
View from 8km up
Huygens probe release into Titan
First extra-solar planet imaged: 2008
Kepler planets February 2011
Planet roughly x3 mass of Jupiter but orbits at a
distance of 115 AU (about x20 distance of Jupiter )
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Selected Missions
Messenger (2004; arrived 2011)
Bepi-Colombo (2016; arrives
2024)
NASA mission to Mercury
Rosetta (2004)
ESA mission to visit comets
Venus Express (2005)
ESA+Japan mission to Mercury
ESA mission to Venus
Corot (France/ESA) (2006)
Kepler (NASA) (2009)
Search for extra-solar planets
New Horizons Mission (2006)
NASA mission to visit Pluto
(2015) and the Kuiper belt
The End
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