QUESTION: With the soil temperature ranging around 60 degrees F, is there essentially a seperate enviornment which exists between ground level and approximately 5 feet from the surface where temperature conditions change drastically? Do the ground temperatures remain stable through the different seasons on Mars? ANSWER from Mike Mellon on August 13, 1997: Ground temperatures and air temperatures generally differ, perhaps more so on Mars because the air is much thinner than Earth's (about 140 times thinner). The surface of a planet absorbs much of the solar energy, where the atmosphere lets the sunlight pass through it. So daytime high temperatures are usually higher for the ground than the air. An extreme example might be walking on the sidewalk or a beach, barefoot on a hot summer day. The air is hot, but the ground is much hotter and you could even burn your feet. Similarly the ground can cool at night, more efficiently than can the air, by infrared radiation. On Earth this can result in a dew or frost forming on the ground where warmer wet air contacts the colder ground (much like water droplets forming on the outside of a glass of ice water). As for seasons, Mars experiences seasons like the Earth because of a similar tilt in its spin axis. The Martian year, however, is about 687 Earth days long. The average temperature on Mars is about -70 centigrade (-94 Fahrenheit). At the poles night time temperatures can fall as low as -125 centigrade (-193 Fahrenheit) at which point the carbon dioxide atmosphere starts to condense on the ground as frost. At the equator in the summer ground temperatures can rise above freezing and even be quite comfortable (to sit on - the air is still quite cold). But the dry atmosphere prevents liquid water from collecting. The Pathfinder spacecraft landed near the equator (19 degrees North latitude) and at a warm time of year at that location (equivalent to late spring). Mike Mellon