astronomy 3 : lecture 14 - lecture

atmosphere of Venus

96% CO2 (carbon), 3.5% N2, small amounts of water and other gases

the dense atmosphere of Venus

its pressure is about 100 times that of Earth’s

the hot atmosphere of Venus (hottest planet)

surface temperatures = 750 K (900 degree F). consequence of runaway greenhouse effect made hydrogen gas escape from Venus into space

slow and retrograde rotation of Venus

its spin is retrograde (backwards). two possible causes are (1) Venus was struck shortly after its birth by a huge planetesimal (2) tidal forces from the Sun and perhaps Earth may have shifted its spin axis over time

surface features of Mars

clear atmosphere and polar caps. home to the largest mountain, Olympus Mons

proof of water on Mars

stream flow

atmosphere of Mars

we know Mars has an atmosphere because of the presence of clouds and dust storms. the atmosphere is mainly CO2, with traces of N2, oxygen and water. but due to its low density, we don’t see the same effect as in Venus even though Mars is made up of mainly CO2

Mars is cold

caused by its thin atmosphere and it being far from the sun. the thin atmosphere makes it hard for it to capture heat. most water is frozen and locked up due to its cold temperature

visuals of Mars

fog seen in valleys and ground frost has been observed. CO2 “snow” falls on poles during winter (proof of water?)

ancient waters about Mars’ ancient atmosphere

Mars had to have a denser atmosphere in order to have water. cratering records supports this. cratering lets us know when the atmosphere disappeared

2 ways Mars lost its thick atmosphere

(1) Mars was struck by a huge asteroid that blasted the atmosphere into space and (2) Mar’s low gravity (due to its low mass) coupled with low volcanic activity produced a net loss of gas molecules into space over the first 1 to 2 billion years of existence, decreasing the effectiveness of the greenhouse effect to maintain a warm atmosphere

the Martian moons

irregularly shaped and small. Deimos is slowly moving away from Mars while Phobos is falling inward due to tidal forces

factors that affect planets’ current state

planet mass dictates whether they have an atmosphere and what shape they are. it also affects how quickly it cools and determines whether magnetic field is present. distance from the sun tells us how much energy they can get (temperature) and how easy it is to retain an atmosphere (create and maintain). also whether water is present

Mercury

Venus

Mars

Jupiter

low density and its atmosphere is mainly H, He, CH4, NH3, and H20. due to its low density we can say that its interior is composed of very light elements

Jupiter’s interior structure

interior becomes increasingly dense with depth, with gas turning to liquid hydrogen. deepere, liquid hydrogen compresses into liquid metallic H. it still has a iron-rocky core because of Juno

Jupiter’s interior

emits more energy than it receives from the Sun due to (1) heat left over from its creation and (2) its may still be shrinking in size so its converts gravitational energy into heat

Jupiter’s outer atmosphere

clouds appear to be particles of water, ice, and ammonia compounds. bright colors of cloud may come from complex organic molecules. jupiter rotates exremely fast!