There are three key environmental factors that set the Moon apart from Earth: its lower gravity, its virtual lack of an atmosphere, and the extreme temperature fluctuations experienced on its surface. Understanding the fluctuations in lunar surface and subsurface temperature is critical for future human and robotic exploration: whereas the Apollo missions all took place during the lunar day and involved landings in equatorial regions, future missions will cover a much wider range of latitudes, and will take place over longer durations. Diviner is currently mapping surface and subsurface temperatures, providing information about potential ice reservoirs and suitable thermal environments for habitation.
With the exception of Mercury, the Moon has the most extreme surface thermal environment of any planetary body in the solar system. At the lunar equator, mean surface temperatures reach almost 400K (260.6 ºF) at noon and then drop to below 100K (-279.4 ºF) during the night. For comparison, the mean surface temperature on Earth is a temperate 295K (71.6 ºF).
The Earth and Moon each receive the same flux of solar radiation; the important difference is that the Moon doesn't have an atmosphere to insulate its surface. In addition to this the lunar day/night cycle lasts ~1 month (compared to 24 hours on Earth). Both of these factors are key in producing the extreme temperatures experienced on the Moon.
|Equator Average Temperature (K)||~206K (390K at noon; ~95 K at midnight)||~299K (303K at noon, ~295K at midnight)|
|Polar Average Temperature (K)||~98K (outside of shadow)||~256K (North Pole) ~230K (South Pole)|
|Minumum temperature (K)||~25K (Hermite Crater)||~184K (Vostok Station, Antartica)|
|Maximum Temperature (K)||~410K (small equatorial craters)||~331K (El Azizia, Libya)|
The spin axis of the Moon is almost perpendicular to the eclliptic plane. The result is that areas of high and low elevation at the lunar poles experience extremes in illumination, with some crater floors remaining in permanent shadow. Diviner has revealed that temperatures within these permanently-shadowed craters can fall as low as 25K (-414.4 ºF). These cold traps present ideal candidates for potential stores of ice on the lunar surface because although the Moon has no indigenous water, molecules are deposited on its surface from comet and asteroid impacts. Evidence of possible ice has been discovered by the Clementine Bistatic Experiment and the Lunar Prospector.
Conversely, some of the crater rims adjacent to these permanently-shadowed regions are high enough that they receive continuous sunlight, and Diviner has observed that temperatures in these regions remain constant at around 220K. This makes them ideal sites for extended surface operations.
Heat flow measurements made during the Apollo 15 and 17 missions (Langseth et al. 1973) revealed that the top 1-2 cm of lunar regolith has extremely low thermal conductivity. The mean temperature measured 35cm below the surface of the Apollo sites was 40-45K warmer than the surface. At a depth of 80cm the day/night temperature variation experienced at the surface was imperceptible. This implies that habitations in the lunar subsurface exist that are not subject to the harsh temperature extremes prevalent on the surface.
The Diviner team will produce and archive a range of data products. These include low-level products derived from instrument telemetry (Level 0); calibrated data with associated geometry (Level 1); and higher-level data products that include gridded temperatures (Level 2); and derived fields such as thermal inertia, rock abundance, and mineralogy that will be created with the aid of topographic data and models (Level 3). Additionaly, the Diviner team will provide specialized data products relating to permanently shadowed regions at the lunar poles (Level 4). These products will be made available to the public online through this web site, and archived through the Geosciences Node of NASA's Planetary Data System.
|Diviner Data Product Level||Description||Archive Delivery Schedule||Size (bytes)|
|Pre-Flight Calibration Data||Pre-flight calibration data (Spectral Response, Blackbody Response, Solar Target Reflectance, Fields of View)||Pre-Launch||<1.00e10|
|Level 0||Depacketized time-sequenced raw science and housekeeping data||Best-available data maintained, archived 6 months after receipt||5.47e+11|
|Level 1||Calibrated radiances and housekeeping data merged with project-supplied geometry and timing information||Best-available data maintained, archived 6 months after receipt||9.86e+12|
|Experimenter's Notebook||Chronological text description of instrument operation and performance||6 months after receipt||<1.00e+06|
|Level 2||Gridded (Lat, Lon, Local time) global surface temperature||Best-available data maintained, archived 5 months after first complete year of mapping orbit||1.20e+09|
|Level 2*||Gridded (Lat, Lon, Local time) global surface temperature and annual max, min and average surface temperature in queryable online database||Best-available version available online - updated monthly, but not archived||1.20e+08|
|Level 3||Gridded derived global fields: Lambert albedo, fine component thermal inertia, anisothermality, rock abundance, silicate mineralogy||Best-available data maintained, archived 5 months after first complete year of mapping orbit||8.80e+08|
|Level 3*||Gridded derived global fields: Lambert albedo, fine component thermal inertia, anisothermality, rock abundance, silicate mineralogy in queryable online database||Best-available version available online, updated monthly but not archived||8.80e+08|
|Level 4||Polar resource products: maps of permanently shadowed regions, localized maps of derived surface and subsurface temperatures, illumination levels, water ice near-infrared reflectance maps for all regions potentially containing cold-trapped volatiles||Best-available data maintained, archived 6 months after first complete year of mapping orbit||4.20e+09|
The Diviner Lunar Radiometer Experiment is funded by NASA through the Lunar
Reconnaissance Orbiter Project at NASA Goddard.
The instrument is built and operated by JPL.