Lyot is a large peak ring crater in the

Vastitas Borealis (Latin 'northern waste') is the largest lowland region of Mars. It is in the northerly latitudes of the planet and encircles the northern polar region. Vastitas Borealis is often simply referred to as the northern plains, northern lowlands or ...

region of Mars, located at 50.8° north latitude and 330.7° west longitude within the

Ismenius Lacus quadrangle The Ismenius Lacus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle is located in the northwestern portion of Mars’ eastern hemisphere ...

. It is 236 km in diameter. Its name refers to

Bernard Lyot Bernard Ferdinand Lyot (27 February 1897 in Paris – 2 April 1952 in Cairo) was a French astronomer. Biography An avid reader of the works of Camille Flammarion, he became a member of the Société Astronomique de France in 1915 and made h ...

, a French astronomer (1897–1952). 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. Lyot is the deepest point in the northern hemisphere of Mars. To the south are the

Deuteronilus Mensae Deuteronilus Mensae is a region on Mars 937 km across and centered at . It covers 344°–325° West and 40°–48° North. Deuteronilus region lies just to the north of Arabia Terra and is included in the Ismenius Lacus quadrangle. It is al ...

, and further to the southeast are

Protonilus Mensae Protonilus Mensae is an area of Mars in the Ismenius Lacus quadrangle. It is centered on the coordinates of 43.86° N and 49.4° E. Its western and eastern longitudes are 37° E and 59.7° E. North and south latitudes are 47.06° N and 39.87° ...

. To the west is the smaller Micoud crater, and to the east-southeast is

Moreux crater Moreux may refer to: * Jean-Charles Moreux (1889–1956), French architect * Théophile Moreux Théophile Moreux (20 November 1867 – 13 July 1954) was a French astronomer and meteorologist. Life Moreux was born at Argent-sur-Sauldre, Cher on ...

Research published in 2009 describes evidence for liquid water in Lyot in the past. 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 . 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 or

obliquity In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orbit ...

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 the

Noachian The Noachian is a geologic system and early time period on the planet Mars characterized by high rates of meteorite and asteroid impacts and the possible presence of abundant surface water. The absolute age of the Noachian period is uncerta ...

and

Hesperian The Hesperian is a system (stratigraphy), geologic system and geologic timescale, time period on the planet Mars characterized by widespread Volcanology of Mars, volcanic activity and catastrophic flooding that carved immense outflow channels acr ...

periods—4 to 3 billion years ago.

Former rivers

Images from

Mars Reconnaissance Orbiter ''Mars Reconnaissance Orbiter'' (MRO) is a spacecraft designed to study the geology and climate of Mars, provide reconnaissance of future landing sites, and relay data from surface missions back to Earth. It was launched on August 12, 2005, an ...

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 wide and tens of kilometers long. ESP 045389 2295lyotchannels.jpg, Wide view of channels in Lyot crater, as seen by HiRISE unser HiWish program ESP 045389 2295lyotchannelstop.jpg, Close view of channels in Lyot crater, as seen by HiRISE under HiWish program ESP 045389 2295lyotchannelsbottom.jpg, Close view of channels in Lyot crater, as seen by HiRISE under HiWish program WikilyotESP 036870 2330.jpg, Curved channel in Lyot crater, as seen by HiRISE under

HiWish program HiWish is a program created by NASA so that anyone can suggest a place for the HiRISE camera on the Mars Reconnaissance Orbiter to photograph. It was started in January 2010. In the first few months of the program 3000 people signed up to use HiRIS ...

Lyot Crater Channels.jpg, Channels in Lyot as seen by

HiRISE High Resolution Imaging Science Experiment is a camera on board the ''Mars Reconnaissance Orbiter'' which has been orbiting and studying Mars since 2006. The 65 kg (143 lb), US$40 million instrument was built under the direction o ...

Lyot-impact-site 740.jpg, Lyot crater with elevations exaggerated showing distribution of channels caused by hot ejecta melting ice.

Dust devil tracks

Many areas on Mars, including Lyot, experience the passage of giant

dust devil A dust devil is a strong, well-formed, and relatively short-lived whirlwind. Its size ranges from small (half a metre wide and a few metres tall) to large (more than 10 m wide and more than 1 km tall). The primary vertical motion is u ...

s. 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.

Gallery

File:MOC2-276 Lyot color.jpg, MGS image with Lyot at top Lyot Mars Crater Dunes.JPG, Lyot crater dunes, as seen by

. Click on image to see light toned deposits and dust devil tracks. File:Gullies on Central Uplift of Lyot Crater.png, Gullies on central uplift of Lyot crater, image reprocessed from HiRISE data. Wikilyotmola.jpg, MOLA map of Lyot and other nearby craters. Colors indicate elevations. File:Lyot Mars Crater Gullies.jpg, Lyot crater gullies, as seen by HiRISE. File:Lyot Mars Crater Channel.jpg, Lyot crater channel, as seen by CTX. Water-carved channels have been spotted in Lyot crater; the curved line may be one.

Interactive Mars map

References

External links