5 January 1996 To: International Mars Watch Electronic Newsletter Recipients Re: Mars News Flash ----------------------------------------------------------------------- CLANCY MILLIMETER OBSERVATIONS INDICATE POSSIBLE GLOBAL DUST ACTIVITY ON MARS: VISUAL CONFIRMATION HIGHLY DESIRED ----------------------------------------------------------------------- Todd Clancy (CU/LASP) reports that observations from Kitt Peak indicate that a large-scale dust storm is likely occurring on Mars. Todd is observing Mars with the 12-m NRAO telescope, measuring atmospheric CO absorption lines at millimeter wavelengths. Normally, under clear atmospheric conditions, there is a large enough temperature difference between the Martian surface and atmosphere to result in the formation of absorption features having high contrast. However, under dusty conditions, the surface-atmospheric temperature difference is smaller, and the absorption feature constrast is substantially decreased. Todd reports that observations from Kitt Peak this week (at Ls=222) reveal lower CO absorption band contrast than usual, indicating an estimated >=20K elevation in the atmospheric temperature above the 10-20 km level. This amount of atmospheric heating is consistent with a global-scale dust storm event, similar in nature though not as large as the events reported by Clancy and colleagues during April 1994 and April 1992. Todd notes that since this storm has apparently just begun (atmospheric heating was not detected in this year's observations prior to Ls=222), it is probably only in the early to mid stages of the dust buildup. Additional millimeter observations are planned for this weekend and later in January in order to confirm the storm and to more accurately quantify the dust opacity. It would be highly desirable to obtain visual confirmation of this dust event, both in order to scrutinize the storm itself as well as to "practice" obtaining the types of groundbased support observations that are needed by the upcoming Mars Pathfinder mission. However, this is a difficult and challenging task, as Mars is currently only 4.0 arcsec in apparent diameter and only 13 degrees from the Sun (and approaching conjunction). Both professional and amateur observers who can observe Mars now are encouraged to do so to try to provide visual verification and additional information about the character of the dust storm. Unfortunately, the Hubble Space Telescope will not be able to observe Mars until September because of solar phase angle limitations. Please pass along this information to interested colleagues, and feel free to send along any questions, comments, or observing progress reports to the email address listed below. ------------------------------------------------------------------------- Jim Bell ----------------------------------------------------------------- Cornell University Department of Astronomy Center for Radiophysics and Space Research 424 Space Sciences Building Ithaca, NY 14853-6801 phone: 607-255-5911 fax: 607-255-9002 email: jimbo@marswatch.tn.cornell.edu WWW: http://marswatch.tn.cornell.edu -------------------------------------------------------------------------