Introduction to the Solar System

Mars at opposition

Remember that giant crack in the crust, projecting SE from the Tharsis Bulge?
It is called Valles Marineris
On this image you can see most of this canyon system
On the middle right you can see dark wind streaks projecting behind craters
There are runoff channels feeding into a huge basin in the upper right

The Viking orbiters took a close look at Valles Marineris
Lots of jumbled up sections, steep, steep walls
25,000 feet deep

Valles Marineris definitely was not formed by water, because we don't see any evidence of sediments
But we do see a lot of carved away cliffs, shown in this oblique image of Candor Chasma

When we look very closely at the cliffs, we see layers at the top, just like layers on the Earth
These may have been put down by volcanic events, or may be rocks that reacted with gases in the atmosphere when it was different (volcanically active)

There is lots of evidence of wind like dust streaks behind craters
Viking also measured winds, and we are getting to understand martian weather with that data and computer models

One thing about the wind on Mars -- it can get very strong
It can get so strong that dust storms kick up during the warmest weather in the south
Most dust storms are local, but they can all combine to cover the planet completely

Rock seen at the V1 landing site
About two meters across, called 'Big Joe'
You can see where sand from dust storms have settled on it
But you can also see where the sand slumped off
This happened while the lander was there -- we saw it before and after

Dust storms came by several times while Viking 1 sat and made its measurements for two years on the surface
This is a series of images (taken at the same time of day) showing how everything got darker during a dust storm

The poles have permanent ice caps --CO2 in the south, water ice in the North
Here's the south polar cap
You can see clouds around it -- often, in the fall, there is a thick ring off clouds where snow falls and increases the size of the caps
You can also see clouds on the morning terminator near the equator -- morning fog

The polar caps grown and shrink with the seasons
But there is a permanent core, that looks like it may have huge ice walls and canyons
This image was taken in the late summer, when the pole is lit up and about to plunge into a midnight sun, when the cap will grow

As the cap sublimates (grows or shrinks), a huge polar vortex of air is generated, circulating about the cap.
you can see how the cap get laid down by the intricate spiral pattern

Because the caps might be sources of water, and give a clue to Mars' climate, Viking looked very hard there
This is near the edge of the N polar cap, where there are probably large cliffs and canyons of ice

There are intricate lines of alternating ice and dirt.
This is evidence for climate change on Mars
There were times when ice was deposited and taken away, and times when dust or dirt was deposited or taken away
The caps have experienced a varying climate

Mars has two very small, asteroid like moons
They are close in to the planet, and may be captured asteroids
This one is the larger of the two, 26 km wide
It has a huge crater on one side, and a series of fractures

The cracks may be related to stresses of a large impact that almost fractured the moon
The moons are so small they would only be specks, whipping around the planet

Although we haven't had any missions in a long time (Mars Observer blew up as it fired its rockets on the way to Mars 3 years ago), we have a new way at looking at Mars
This is a Hubble Space Telescope image of Mars
We can watch it now over the long term, and look at weather patters, shifing regions of dark and light, dust storms, and polar cap changes

NASA has been told, "cheaper, faster, better". Apollo cost $22 B in 1970 dollars. Viking cost $2.2 B, same as Hubble, Voyager
New missions will cost no more than $150 M and have more risk
Some people say it is too cheap, and call it "cheaper, better, never"
But we have an ambitious plan now to send small spacecraft to Mars, one every year up to 2005.
2005 might be a sample and return mission
The next one is Pathfinder, launching in Dec of this year
Arrive July 4, 1997 after 7 month journey
It's going to land somewhere in this ellipse, in a place where liquid water once flowed

It has a lander with color stereo cameras, and a tiny rover
Rover has a camera and a probe to measure the composition of rocks
Very minimal mission, but cheap and effective--the way NASA wants to go

But there's a whole new way of studying Mars that we've been busy at while there have been no mission
We have pieces of Mars?
They were found in various places on Earth -- Africa, Antarctica
One came down in Egypt and killed a dog
The only known fatality from a falling rock
Large impact on Mars spewed out rocks that ended up on the Earth
We know they are from Mars because tiny gas bubbles trapped in the rock are exactly like the martian atmosphere as measured by Viking Landers
Details of the different isotopes, particularly O2, clinched it. No O2 isotopes like that on the Earth, only Mars
Panspermia -- computer models show that some rocks can be blasted into space and stay cool enough to harbour life
Bacteria may exist as spores in space for 100 My
They can even survive reentry
Panspermia is the theory that says it is possible for life to transport between planets
Life probably made it from Earth to Mars

6/17/96