8.1 FANTASIES OF MARTIAN CIVILIZATION
How did Mars invade popular Culture?
Began by William Hershel and Sister Caroline, two astronomers who discovered Uranus.
They discovered the length of Mars days, (24.5 hrs) and saw ice caps.
Claimed that Mars possessed an atmosphere.
For some reason they just assumed that that every planet is inhabited.
Later Giovanni Schiaparelli looked at Mars from a telescope.
He saw networks and channels, canals called Canali, which is italian for channels.
People were excited that maybe there are artifical waterways built by alien civilization.
He was skeptical about it.
Percival Lowell believed in the idea of water canals.
Built observatory in Flagstaff that's really high and has dry air. This is ecause he thinks if the observatory is too low it will distort the view because of the atmosphere.
He said that the canals must be used to carry water from the pole to cities.
From here there was a leap to image the Martians as an old civilization on a dying planet. It became a widespread idea especially since the publish of The War of the Worlds, a
movie about Martians.
Flaw: There was no canals. Most astronomers could not see canals when they put their eyes to the telescope
Alfred Russel Wallace was the one that said there were no canals.
He also said that there's so cold it can't have any water.
Also said that the canals can't be straight lines that run for miles, as Lowell believed.
Argued for cold mars, a mars that has only ice.
All his arguments come from topography: So it should follow natural contours and go around mountains.
In truth the canals are canyon networks, at this area called Valles Marineris. (One of the few that wasn't a fantasy)
8.2 MODERN PORTRAIT OF MARS
1965: NASA’s Mariner 4 spacecraft flew to within 6000 miles of the martian surface, transmitting a few dozen televisionquality images of the landscape below.
Surface: littered with craters, not canals.
Atmosphere: A cold, dry planet seemingly incapable of supporting life.
Possibilities: the thin atmosphere and the polar caps left open the possibility of the existence of microbes or perhaps even some primitive plants or animals.
Viking 1: A lander that tuched down at Chryse Planitia,
Viking 2: Landed 2 months later on the other side.
Discoveries: Bleak landscape with red dust and scattered rocks. Occasional frost and dust. Collected soil for some experiments. Phobos 1, Phobos 2 are 2 russian missions.
Mars Observer observer is a USA mission
These too all failed.
Pathfinder: Succeeded in landing and checked the chemical compositions of the martian rocks.
What is Mars like Today?
Surface of Mars = some deserts or volcanic plains on Earth
Surface temperature = well below freezing
Atmospheric pressure = less than 1% that on the surface of Earth, too thin.
Air = no oxygen, we can't breathe there.
No oxygen = no ozone = no uv protection
Gravity = 40% of Earth
No liquid water exists anywhere on the surface of Mars today.
Mars is so cold that any liquid water would immediately freeze into ice.
Sometimes temperature is above freezing point, but no atmosphere means the liquid water evaporates easily.
If you put on a space suit and took a cup of water outside your pressurized spaceship, the water would almost immediately either freeze or evaporate away.
It had liquid water in the past, some water ice now, and maybe even liquid water underground.
Mars has similar season to Earth. It was a 25degree tilt rather than 23.5 degree.
But it differs in 2 different ways:
1. Martian year is twice as long as Earth, so each season lasts twice as long.
2. Second, while Earth’s nearly circular orbit means that tilt is the only significant factor in our seasons, Mars’s seasons are also affected by the ellipticity of its orbit. Mars is
significantly closer to the Sun during its southern hemisphere summer and farther from the Sun during its southern hemisphere winter
Mars’s southern hemisphere has more extreme seasons (shorter and warmer summers, longer and colder winters) than its northern hemisphere.
The season changes lead to several major features : temperatures at the winter pole drop so low that carbon dioxide condenses into “dry ice” at the polar cap.
In the summer there are only Frozen carbon dioxide in the summer, so the polar cap is much smaller.
Overall, as much as onethird of the total carbon dioxide of the martian atmosphere moves seasonally between the north and south polar caps.
The strong winds associated with the cycling of carbon dioxide gas can initiate huge dust storms, particularly when the more extreme summer approaches in the southern
At times, the martian surface becomes almost completely obscured by airborne dust.
Dust devils: swirling winds like mini tornados that rise from the ground. They come from rising air that art with prevailing winds.
Color of the sky is essential black during the day time, but the light scattered by the dust gives the sky a yellow brown colour.
What are the major geological features of Mars?
Many surface features appear to have been shaped by liquid water, leading scientists to conclude that Mars must once have had a much more hospitable climate. Mars is about half as large in diameter as Earth, so its surface area is about onefourth that of Earth.
Because water covers about threefourths of Earth’s surface, the total land area of Mars is about the same as the total land area of Earth.
Much of the southern hemisphere has relatively high elevation and is scarred by numerous large impact craters, including the very large crater known as the Hellas Basin.
In contrast, the northern plains show few impact craters and tend to be below the average martian surface level. This might be smoothed out because of geological processes.
Therefore, south is older than north: Because everywhere was bumpy but recent lava flow smoothed the north. (and due to tectonics and erosion)
Interestingly, we can see faint “ghost” craters in some of these regions, suggesting that the lava flows were not thick enough to completely erase the underlying features and
confirming that the entire planet was once densely cratered.
Some of the volcanoes are like the size of a continent, like the Tharsis Bulge.
Rises several km above ground level. Created by a longlived plume of rising mantle material that bulged the surface upward and provided the molten rock for the eruptions that
built the giant volcanoes.
Two reasons why it was so big: less gravity helps it to build up. And lack of plate tectonics means less likely to get bumped into mini bumps or fall down.
On Earth, a single plume makes a chain of volcanic islands. On Mars, a plume makes one big mountain because the gravity on Earth does not raise the mantle enough, so it
must spread out.
East of Tharsis and just south of the equator is the long, deep system of valleys called Valles Marineris. As long as the USA and 4 times as deep as the grand Canyon.
No one knows why it was formed, maybe tectonic stresses after the Tharsis was lifted?
It has evidence of flowing water, but it could be just lava flows.
It's so deep that its walls must have been once so deep underground that it was exposed to liquid water.
Therefore it's the best place to search for Martian life. Looking at these geological features, we see what geological
process shaped Mars:
Looking at laval flows and volcanic eruptions. Shows that the
frequency of volcanic eruptions on Mars has decreased steadily
since at least about 3.5 billion years ago. (Of course, it must
have lost much of its internal heat by now.)
Looking at meteorites that came from mars: Radiometric dating
shows that some are made of volcanic rocks 180 million years
ago, so pretty recent.
No one knows if there's internal heat for more volcano
eruptions, but it should be enough to melt underground ice into
What evidence tells us that water once flower on Mars?
1. Orbital evidence: Came from Mariner 9 and viking, showed features like dry riverbed pictures. They must have been carved from water, but its possible that it was just water
from rainfall. They're 23 billion years old, so it's pretty darn old. They branch in a way that tells us that it was very stable liquid water.
Past liquid water = past atmosphere = water and better climate in the past
2. Impact crater evidence: Rims of craters are eroded and lack of small craters imply rainfall.
But it might be from wind or glaciers. Some crater bottoms have things that look like lake craters.
From these images, we found hydrated minerals.
These are minerals containing water, which indicates water presence. These minerals include clay, hydrated sulfates and opal.
Opal minerals are the most significant: Their presence are significant because they for in hots springs, and these are important environments for life. These regions formed later
than clay deposits, so it means Mars remained wet for a long time in history. 3. Rover evidence = There are two robotic rovers named Spirit and Opportunity. and they discovered hematite.
Opportunity found hematites..
This is an iron rich mineral that forms in water, but can also form in volcanic processes.
They found rocks that are called hematite spheres, aka blueberries, that are like very similar to hematite spheres found on Earth in water.
Spirit found hydrated sulfates, in this region called Home Plate.
With other clues it is likely that this region was a volcanic heated hot spring.
Mars shows evidence of having suffered catastrophic floods.
Ares Vallis = place that has outflow channels that look like it was carved by floodwaters. Tracing it leads to nothing, so the water probably came from underground.
Some other land however, shows flood marks similar to that on Earth.
There seems to be some connection between these water and volcanic activities. Significant because water + heat = life
To estimate how much water might once have flowed on Mars, scientists can look at water ice that still exists today.
Water seems widespread in the arctic, mixed with the surface of soil or hidden under dust.
In there northern plains there seem to have had an ocean in the past, or rainfall just left a filled ocean basin. Scientific controversy about if there was an ocean in the first place.
Whether Mars ever had an atmosphere warm enough and thick enough to make liquid water stable on the surface. If it didn’t, then water flows could only have been intermittent,
and lakes or oceans could not have lasted the millions of years which would be necessary for life to arise.
We have found no evidence pointing to largescale water flows on Mars during the past billion years or so.
The most intriguing hints of recent water flows come from photos of gullies on crater and channel walls. These gullies look strikingly similar to those that form after rainfall on
almost any eroded slope on Earth.
It can be from melted snow, or just landslides.
8.3 The Climate History of Mars
95% of its atmosphere is composed of greenhouse gas carbon dioxide, but it still has a thin atmosphere and a week greenhouse effect.
Martian volcanoes should have outgassed enough carbon dioxide to make the atmosphere about 400 times as dense as it is today.
If Mars had this much carbon dioxide today, it would have a surface pressure about three times that of Earth and a temperature above freezing—in other words, a
climate in which liquid water could flow. It's too thin now.
But the sun was probably more dim in the past and even more greenhouse effect would have been needed for liquid water to be present.
But liquid water WAS present (we think) so where was the additional greenhouse gas from?
We think it is from carbon dioxide ice clouds or methane gas, or maybe it was just the heat from large impacts for intermittent wet periods.
Anyways, the evidence we’ve found for extensive water flows means that Mars’s atmosphere must have been much thicker and warmer in the distant past than it is
Why did Mars Change?
It had plenty of water and carbon dioxide in the beginning from volcanism and outgassing.
It somehow lost a vast quantity of carbon dioxide gas, which weakened the greenhouse effect until the planet essentially froze over.
Most of it was lost to space. The precise way in which Mars lost its carbon dioxide gas is not clear, although some gas was almost certainly blasted away by large impacts.
Recent data suggest that an even more important loss mechanism was linked to a change in Mars’s magnetic field.
It used to have a strong magnetosphere to protect its atmosphere. It weakened as the small planet cooled and that is how solar wind stripped away the Carbon
dioxide gas. Same thing with water, stripped away.
Water was also lost in another way: Because Mars lacks an u