Lesson4b

The Case for water on Mars

Viking – And the Face

The Martians were BACK!

New Data – Higher resolution

3-D Projection

• Extraordinary claims requires extraordinary evidence. (Carl Sagan)

Today on Mars there is no liquid

Today on Mars there is no liquid water in the form of rivers, lakes or oceans.

Why is there no liquid water on Mars?

.1. It is too cold, all water is frozen

2. It is too hot, all water is a gas3. The pressure is too low for

liquid water4. Mars is a dry world like the

Moon

Temperature on Mars

• Although the temperature is very cold on Mars (-200o F at the poles during winter) the temperature can reach as high as 80o F near the equator during the day.

• So temperatures frequently go above freezing on Mars.

This is a water phase diagram– Pressure verses Temperature

• If you are high in the mountains and you decide to boil water in a pan, what will happen?

.1. Water would boil at a lower temperature

2. Water would boil at a higher temperature

3. What wouldn’t boil at all because the pressure is wrong.

Phase diagram for water

• At high altitudes water boils at a lower temperature than at sea-level.

• What about carbon dioxide?

Phase diagram for C02

• At one Earth atmosphere pressure there is no temperature where CO2 is a liquid.

• Martian atmospheric pressure is 0.006 that of the Earth’s atmosphere at sea-level.

• Let’s look at the water phase diagram again.

On Mars the atmospheric pressure is too low for liquid water.

• On Mars water either exists as ice or as what vapor.

• When the temperature gets high enough the ice sublimes directly to gas.

• This prevents liquid water from existing on the surface of Mars.

A history of Mars through fluid flow (water?)

Large ancient outflows that

begin in chaos regions

Large outflow regions

• http://www.google.com/mars/

Dendriticdrainage valleys

found in hilly regions

Dendritic Drainage Valleys

Characteristics of fluid flowRiver meander

What causes a river to meander?

• As water flows along the surface it always flows to the lowest level. This is because gravity is the force causing the water to flow.

• The path of water flow is initially dictated by the contour of the ground that the water is flowing over.

What will happen to the water’s speed as it approaches the curve?

What will happen to the water’s speed as it approaches the curve?

.1. The water on the outside of the curve will move more slowly than the inside of the curve

2. The water on the outside of the curve will move more rapidly

3. Water is a liquid so it will all move at the same speed

What will happen to the water’s speed as it approaches the curve?

Fast moving water

Slow moving water

Fast moving water erodes soil more effectively

As Time goes by

Characteristics of fluid flowRiver meander

Other characteristics

Cut Bank

Deposition Bar (Sand bar)

• A deposition bar is composed of rocks, sand and dirt that is carried along in the water flow.

• Where should you expect a deposition bar to form in a river?

.

1 2 3

0% 0%0%

1. Where the water moves the slowest because debris will drop out of the water

2. Where the water moves the fastest because it can then carry debris

3. Usually on the outside of the curve

Other characteristics

Cut Bank

Deposition Bar (Sand bar)

Deposition bar is always on the inside curve of a river

• Fast moving water on the outside curve cuts into the river bank and creates a cut-bank.

• Slow moving water on the inside curve drops material carried by the water forming a deposition bar.

• Over time the cut-bank erosion moves the river farther out, and the deposition fills in as the curves become more pronounced.

Eventually curve can become pinched off and oxbow lake forms

Mars from the HiRISE Camera

Wind erosion

Harder river bed material

Which is older, the river bed or the surface around the river bed?

.

1 2 3

0% 0%0%

1. The surface surrounding the river bed, because the bed is on top.

2. The river bed because it flowed over the surface around it.

3. The river bed. It has a greater crater density.

The river bed is older. Crater density is higher.

Ancient meander on Mars

Dendritic (tree-like) drainage valleys

Earth Mars

• When ground slope is steep water runs quickly in small streams, which eventually run together to form a tributary system for the main river.

Stream-lined islands

Stream-lined islands

Fluting – Longitudinal lines caused by fluid flow

Changes in water level

Large outflowsThey look like

enormous flooding events, but they are not tied to

tributary systems like we would see

on Earth where water comes from

precipitation

SourceChaos

Regions

Sapping Springs

Very hard Caprock

Softer rock like sandstone

Sapping Springs

Sapping Springs as time goes by

Very hard Caprock

Softer rock like sandstone

Sapping Springs

Sapping Springs as time goes by

Very hard Caprock

Softer rock like sandstone

Sapping Springs

Fracture

Sapping Springs as time goes by

Very hard Caprock

Softer rock like sandstone

Sapping Springs

Fracture

Chaos

Water appears to come from underground sources