 Shaded relief topographic map of Lyot | |
| Planet | Mars |
|---|---|
| Region | Ismenius Lacus quadrangle |
| Coordinates | 50°48′N330°42′W / 50.8°N 330.7°W /50.8; -330.7 |
| Quadrangle | Ismenius Lacus |
| Diameter | 236 km (147 mi) |
| Eponym | Bernard Lyot, French astronomer (1897–1952) |
Lyot is a largepeak ring crater in theVastitas Borealis region of Mars, located at 50.8° north latitude and 330.7° west longitude within theIsmenius Lacus quadrangle. It is 236 km in diameter. Its name refers toBernard Lyot, a French astronomer (1897–1952).[1]
Lyot crater, featuring a central peak in the middle, stands out on the flat plains of Vastitas Borealis, which is generally flat and smooth with few large craters.[2] Lyot is the deepest point in the northern hemisphere of Mars.[3][4][5]
Being so low in elevation Lyot would have a high relative surface pressure within a restricted. Lyot has a microenvironment[6] That is climate in a small area that is different to that of the surroundings.[7][8] Consequently, stable liquid surface water (i.e. surface pressure and temperature are above the triple point of water; see Section 3) may occur during its lifetime.[9]
To the south are theDeuteronilus Mensae, and further to the southeast areProtonilus Mensae. To the west is the smallerMicoud crater, and to the east-southeast isMoreux crater.
Research published in 2009 describes evidence for liquid water in Lyot in the past.[10]
Many channels have been found near Lyot Crater. Research, published in 2017, concluded that the channels were made from water released when the hot ejecta landed on a layer of ice that was 20 to 300 meters thick. Calculations suggest that the ejecta would have had a temperature of at least 250 °F (121 °C). The valleys seem to start from beneath the ejecta near the outer edge of the ejecta. One evidence for this idea is that there are few secondary craters nearby. Few secondary craters were formed because most landed on ice and did not affect the ground below. The ice accumulated in the area when the climate was different. The tilt orobliquity of the axis changes frequently. During periods of greater tilt, ice from the poles is redistributed to the mid-latitudes. The existence of these channels is unusual because although Mars used to have water in rivers, lakes, and an ocean, these features have been dated to theNoachian andHesperian periods—4 to 3 billion years ago.[11][12][13]
Modelling supports the idea that Lyot went through a great deal of fluvial activity However, it would not have all happened at the same time. Water erosion took place at different times in different parts of the crater. During periods when water was not stable, it would have boiled or frozen. But although if the water was deep enough, a layer of ice on the surface of the water could have protected the liquid water underneath. Water would then flow again when conditions were suitable.[14]
Images fromMars Reconnaissance Orbiter show valleys carved by rivers on the floor of Lyot crater. Scientists are excited because the rivers seem to have formed more recently than others on Mars; water could have flowed in them only 1.25 million years ago. The source of the water is believed to have been ice from nearby glaciers. The river valleys are over 250 metres (820 ft) wide and tens of kilometers long.[15]
Many areas on Mars, including Lyot, experience the passage of giantdust devils. A thin coating of fine bright dust covers most of the Martian surface. When a dust devil goes by it blows away the coating and exposes the underlying dark surface. These dust devils have been seen from the ground and high overhead from orbit.
