NASA's Mars Odyssey spacecraft found seven possible cave entrances on Mars, US space agency reported.

Images showed dark, nearly circular spots between 100 meters and 250 meters wide on the slopes of the Arsia Mons volcano, located near the Red planet's highest peak.

Researchers concluded that the seven circles could be windows to underground spaces after checking their daytime and nighttime temperatures by using Odyssey's infrared camera.

The discovery of the holes, dubbed "Seven Sisters," has triggered interest in further hunting for caverns elsewhere on the planet.

"Somewhere on Mars, caves might provide a protected niche for past or current life, or shelter for humans in the future," researcher from US Geological Survey's Astrogeology Team explained.

Arizona State University operates Mars Odyssey's Thermal Emission Imaging System, which was used to detect the potential cave entrances.

Odyssey reached Mars in 2001.

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