Slipher is an
impact crater
An impact crater is a circular depression in the surface of a solid astronomical object formed by the hypervelocity impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal collapse, impact craters ...
in the
Thaumasia quadrangle
The Thaumasia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Thaumasia quadrangle is also referred to as MC-25 (Mars Chart-25).
The name comes fr ...
of
Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury (planet), Mercury. In the English language, Mars is named for the Mars (mythology), Roman god of war. Mars is a terr ...
, located at 47.3°S latitude and 84.6°W longitude. It measures in diameter and was named after American astronomers
Vesto and
Earl Slipher
Earl Carl Slipher (; March 25, 1883 – August 7, 1964) was an American astronomer, and politician. He was the brother of astronomer Vesto Slipher. He served in both the Arizona House of Representatives and the Arizona State Senate.
Biography
S ...
. The naming was approved by IAU's
Working Group for Planetary System Nomenclature
The International Astronomical Union (IAU; french: link=yes, Union astronomique internationale, UAI) is a nongovernmental organisation with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach ...
in 1973.
Description
Gullies are visible on the walls of a crater that is on the rim of Slipher. They can be seen in the pictures below.
Martian gullies
Martian gullies are small, incised networks of narrow channels and their associated downslope sediment deposits, found on the planet of Mars. They are named for their resemblance to terrestrial gullies. First discovered on images from Mars Global ...
are small, incised networks of narrow channels and their associated downslope
sediment
Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...
deposits, found on the planet of Mars. They are named for their resemblance to terrestrial
gullies
A gully is a landform created by running water, mass movement, or commonly a combination of both eroding sharply into soil or other relatively erodible material, typically on a hillside or in river floodplains or terraces. Gullies resemble lar ...
. First discovered on images from
Mars Global Surveyor
''Mars Global Surveyor'' (MGS) was an American robotic space probe developed by NASA's Jet Propulsion Laboratory and launched November 1996. MGS was a global mapping mission that examined the entire planet, from the ionosphere down through the a ...
, they occur on steep slopes, especially on the walls of craters. Usually, each gully has a
dendritic
Dendrite derives from the Greek word "dendron" meaning ( "tree-like"), and may refer to:
Biology
*Dendrite, a branched projection of a neuron
*Dendrite (non-neuronal), branching projections of certain skin cells and immune cells
Physical
* Dendr ...
''alcove'' at its head, a
fan-shaped ''apron'' at its base, and a single thread of incised ''channel'' linking the two, giving the whole gully an hourglass shape.
[Malin, M., Edgett, K. 2000. Evidence for recent groundwater seepage and ]surface runoff
Surface runoff (also known as overland flow) is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. This can occur when th ...
on Mars. Science 288, 2330–2335. They are believed to be relatively young because they have few, if any craters. A subclass of gullies is also found cut into the faces of sand dunes which themselves considered to be quite young.
On the basis of their form, aspects, positions, and location amongst and apparent interaction with features thought to be rich in water ice, many researchers believed that the processes carving the gullies involve liquid water. However, this remains a topic of active research.
As soon as gullies were discovered,
researchers began to image many gullies over and over, looking for possible changes. By 2006, some changes were found. Later, with further analysis it was determined that the changes could have occurred by dry granular flows rather than being driven by flowing water. With continued observations many more changes were found in Gasa Crater and others.
With more repeated observations, more and more changes have been found; since the changes occur in the winter and spring, experts are tending to believe that gullies were formed from dry ice. Before-and-after images demonstrated the timing of this activity coincided with seasonal carbon-dioxide frost and temperatures that would not have allowed for liquid water. When dry ice frost changes to a gas, it may lubricate dry material to flow especially on steep slopes.
In some years frost, perhaps as thick as 1 meter.
File:Slipher crater 053A56.jpg, Viking Orbiter 1 image with Slipher crater at bottom
File:Wikislipher.jpg, Slipher crater on Mars, as seen by MRO's CTX camera
File:Wikisliphergullies.jpg, Gullies in crater on the rim of Slipher. This is an enlargement of the previous image.
File:Pedestal crater in Slipher crater F04 037244 1323 XN 47S085W.jpg, The small pedestal crater in the northwestern floor of Slipher
See also
*
List of craters on Mars
__NOTOC__
This is a list of craters on Mars. Impact craters on Mars larger than exist by the hundreds of thousands, but only about one thousand of them have names. Names are assigned by the International Astronomical Union after petitioning by ...
References
{{Geography of Mars
Thaumasia quadrangle
Impact craters on Mars