AS101 Week 10 Lecture 2
Distance from Sun: 1.5 au
Diameter: 6790km (0.53 of Earth's)
Orbital Period: 687 days
Rotation period: 24.6 hours
o Rotation period is close to Earth day
Average Surface Temp: -63C
95% carbon dioxide
Much thinner than Earth's: less than 1% of the density.
What influences a planet's atmosphere?
Size matters: larger planets have stronger gravity and can more easily hold onto gases.
Temperature also makes a difference. (Hotter planets lose their atmospheres more
Volcanic activity (outgassing) can add to or replenish an atmosphere.
On Earth, life plays a big role.
Mar's moons: Phobos and Deimos
Small and irregularly shaped (less than 30km across)
May be captured asteroids: composition appears to be different from the planet.
Greek words for fear and terror
Mars: History of Exploration
First successful flyby: Mariner 4, 1965
First landings: Mars 2+3, 1971
Viking 1+2, 1975 About 40 missions so far
Currently Active: Curiosity rover
Sunset on Mars
Sunset looks blueish whereas rest of Martian sky has redish colors
Reversed from Earth’s colors
Why is Martian Sunset Blue?
On Earth, red light is enhanced and more of the blue light is getting out of the way, while
this is opposite on Mars
Water on Mars
Very little water vapour in the atmosphere, and liquid water cannot exist on the surface
because of the low pressure.
Might have been life at one time
But ice exists a short distance below the surface, and polar ice caps consist of a mixture
of water ice and frozen carbon dioxide (dry ice).
Surface features resembling water erosion on Earth, along with microscopic features in
some rocks, suggest that there was liquid water earlier in the planet's history.
Evidence that there might have been water before
Life on Mars
No sign of it now.
Could there have been life earlier, when there was liquid water?
So far, no clear evidence of it.
In 1996, a paper in Science by David MacKay suggested that a meteorite believed to be
from Mars contained evidence of fossilized bacteria, but this interpretation remains
Mars Curiosity River
Launched Nov. 26, 2011, landed Aug. 6, 2012
About the size of a car. Goals include looking for evidence of present or past life.
Carries multiple cameras, a drill, laser “drills,” miniature laboratories to analyze rock and
Curiosity Landing Site
Landing site was selected in part because it is likely to have been a lakebed when Mars
Some Curiosity Findings
Clay minerals, other minerals that usually form in wet environments on Earth