Water On Mars
Water On Mars
It is currently believed that Mars went through as many as 3 drastic climatic swings in its history. During one of these swings permafrost and ice deposits caught deep under the regolith (left from polar wandering) eroded the surface when melting.This would have caused a catastrophic flood. There are some objections to the catastrophic flood explanation. There are no obvious deposits at the ends of the channels; all the material that was eroded away by the flood would have presumably been left there, but it is not seen in the orbital photos. In addition, the volumes of the source areas don't seem to be large enough to account for all the water that would have been required to erode the affected areas, based on models of the efficiency of erosion by water.The United States Geological survey estimates that the amount of water needed to make to create these many enormous channels would have been enough to fill the a global Martian ocean 500 meters deep. One source for that great quantity of water may have been a deep lake in Valles Marineris (a region on Mars partially covered with sedimentary layers that appear to be ancient lake deposits). Above is a map of the outflow channels in red and valley networks in yellow.
 Some scientist believe features like
this show the shorelines of ancient sea's and oceans. These shorelines are
at the mouth of the huge Valles Marineris canyon which is seen on the bottom
of the image on the left. On either side of Valles Marineris there are signs
of ancient river beds.  There are shorelines
around high ground creating island-like features. These are all key signatures
of the presence of water when Mars' climate was much like Earth's. Imagine
the abundance of sea life that could have lived there. It is believed that
no polar caps were present during the time water flowed freely on the surface.
Only when the catastrophic event(s) occurred which changed the planets biology
liquid water could not survive so it froze and the water was concentrated
at the poles. Then because of the immense weight of an object like Olympus
Mons and the lack thereof in Valles Marineris the crust shift because it
is off balance. |
 Valley networks occur throughout
the older heavily-cratered terrains. The image on the right is of an eroded
Valley network extending out from a believed coast line in Chryse Planatia.
This image on the left shows that over millions of years the land was cut
up by this river and its tributaries. To the left is a wide view of Noctus
Labyrenthus which is a valley network.  As can be seen in the
initial map, most of the outflow channels are isolated to a fairly small
area of the planet, in the younger terrains on Mars. In contrast, the valley
networks are present over almost half the planet, mostly in the ancient
heavily-cratered southern highlands. The valleys can be loosely divided
into two subtypes: long, winding valleys with few tributaries, and smaller
valley networks, often with complex,  multiply-branched patterns of tributaries. A good
example of the first is Nirgal Vallis, south of the eastern part of Valles
Marineris (lower left). A good example of a small valley network (right)
found at latitude 42 south, 93 west in the Thaumasia region. Superficially,
the valley networks resemble river-cut valleys on Earth, and initial speculation
focused on this explanation for them. Despite the fact that there is no
running water or rain on Mars at the present time, earlier in Martian history
such conditions might have prevailed. However, on further examination, there
are significant differences between the Martian valleys and river valleys
on Earth. First and most important, a terrestrial river valley contains
a river, or at least a dry river bed, and no such features have been seen
on Mars at the resolution limit of our current images. (It is important
to note that a valley is not a channel -- the fluid never filled
the valley up to its rim, but was carried only in the channel that cut the
valley over time.) In addition, even the densest tributary networks
on Mars are much sparser than their terrestrial counterparts. These facts
argue against a purely running-water origin for the Martian valleys. |
As one can see from the map at the top of the page,
most of the outflow  channels
are in northern lowlands north of Valles Marineris, just west of the Chryse
region, landing site of Viking Lander 1. The  geometry of the
Martian outflow channels indicate that water could have flowed along the
surface as rapidly as 75 meters per second (170 miles per hour). The outflow
channels are large, often more than 100 km wide and as much as 2000 km long.
They emanate from cracked or jumbled terrain (termed chaotic terrain)
and have distinct flow features such as eroded craters with teardrop-shaped
tails, scour marks, and "islands".  The image on the left clearly depicts these islands.
We mentioned Earlier that at some time there was a mass melting of permafrost
taking land with it. So when this permafrost melted it sunk the land that
it layed under. On the right this image shows what appears to be the source
of the Tiu Vallis outflow. You can see in the enlarged version the sunken
and broken land that layed upon the permafrost until its melting.Not all
of the outflow channels start in chaotic terrain; some, such as Mangala
Vallis, appear to start at deep cracks known as grabens. On the lower
right is a view of Mangala Vallis. Above the two craters is a horizontal
crack. This is a graben. It is believed that while the planet was
heating a crack was formed allowing water a way to exit. |
Chaotic sunken terrain Click here to see the Outflow channel at the mouth of this chaotic terrain. It has extensively layered deposits |
Layered Terrain in a Valley Network |
|
