Martian lava tube

The second method of possible identification is through observation of cave "skylights" or pit craters, which appear as dark, nearly circular features on the surface of Mars.

[2][3] In June, 2010, a group of seventh grade science students at Evergreen Middle School in Cottonwood, California, participating in the Mars Student Imaging Project, helped researchers discover a new series of lava tubes near Pavonis Mons through identification of a skylight estimated to be 190×160 meters wide and at least 115 meters deep.

[9] Lava tubes represent prime locations for direct observation of pristine bedrock where keys to the geological, paleohydrological, and possible biological history of Mars could be found.

The surface of Mars experiences extreme temperature fluctuations and receives a high amount of Ionizing radiation due to the lack of a magnetic field and the planet's thin atmosphere, which is about one one-hundredth (or 1 percent) the thickness of Earth's.

The thin atmosphere allows Mars to radiate heat energy away more easily, so temperatures near the equator can get up to 21 °C (70 °F) during a summer day, and then drop down to −73 °C (−99 °F) at night.

[1] Scientists are also interested in gaining access to Martian lava tubes because they could give insight into the processes that led to life on Earth since the geologic rock record is better preserved on Mars.

[13] The interior of lava tubes, along with other subsurface cavities, could prove to be prime locations for future crewed missions to Mars by providing shelter for habitats.

[1] These natural caverns have roofs estimated to be tens of meters thick which would provide protection from the extreme conditions that would be experienced on the surface.