Water on Mars any point in the year but would be ideal for solid carbon dioxide. The carbon dioxide melting in the warmer summer would yield liquid carbon dioxide which would then form the gullies. Even if gullies are carved by flowing water at the surface, the exact source of the water and the mechanisms behind its motion are not understood. The dry gullies are deep grooves etched into the slopes that are there year-round. There are many other features on Mars, and some of them change seasonally. In August 2011, NASA announced the discovery by undergraduate student Lujendra Ojha of current seasonal
Life on Mars or after a sudden release of underground water. So far, NASA has pursued a "follow the water" strategy on Mars and has not searched for biosignatures for life there directly since the "Viking" mission. As of 2017, the consensus by astrobiologists at NASA is that it may be necessary to access the Martian subsurface to find currently habitable environments. Curiosity measured ionizing radiation levels of 76 mGy a year. This level of ionizing radiation is sterilizing for dormant life on the surface of Mars. It varies considerably in habitability depending on its orbital eccentricity and the tilt of its axis.