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Lecture 1

ASTA01H3 Lecture Notes - Lecture 1: Solar Wind, Star System, Flattening


Department
Astronomy
Course Code
ASTA01H3
Professor
Parandis Tajbakhsh
Lecture
1

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Why did Mars Change?
Volcanic outgassing provided the young Mars with an atmosphere 400 times denser than
Mars’s present atmosphere.
Consequently, Mars should have had a strong green house effect in the past which
in turn made its climate more hospitable.
Mars however has lost a huge quantity of CO2 as well as water.
So far, there is not enough evidence to show an abundance of carbonaceous rocks on
Mars so we cannot conclude that water washed CO2 from the atmosphere.
So Mars has lost a significant part of its atmosphere.
Loss of Atmosphere on Mars
How did Mars end up with such thin atmosphere?
Smaller escape velocity : huge impacts will throw atmosphere gases into space
Lack of ozone layer: UV radiation from the Sun breaks water molecules.
Hydrogen escapes while Oxygen if not lost reacts and form oxides
Solar wind stripping: As Mars cooled, it lost its magnetosphere and thus became
vulnerable to solar wind which keeps stripping off gas from the atmosphere.
The Outer Solar System
Jupiter, Saturn, Uranus and Neptune are called the Jovian planets.
AS of 2015, the Jovian planets have 165 moons altogether.
Jupiter and Saturn are called gas giants while Uranus and Neptune are called ice
giants.
The Jovian Planets
Jovian planets have no solid surface. As one descends down the clouds, temperature
and pressure rise and there is a slow transition from gas to liquid without a sharp
boundary!
Jupiter
The centre of mass of the Sun and Jupiter orbit is just above the surface of the Sun.
Jupiter is the largest planet in the solar system and houses more than 71% of the
planetary mass of our stellar system.
Jupiter and Saturn are both slightly flattened at the two poles.
Oblateness is defined as the fraction by which equatorial diameter exceeds the polar
diameter.
Oblateness is a hint to the large liquid interior
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