Friends of Mars,

Items in this (woefully late and much too large) Marswatch newsletter:

CONTENTS---
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- Latest HST images of Mars: Chaotic climate!
- Schedule for next HST Mars images
- Online Mars image archive a spectacular success!
- Announcement for Mars Telescopic Observations Workshop 2
- Leonard Martin 1930 - 1997
- Detailed HST Mars press release text
- Additional information on Mars Workshop

Recent HST images of Mars from March 1997 have just become available in a press release from the Space Telescope Science Institute. These images, combined with recent microwave telescopic results, indicate that the Martian climate appears to oscillate between two primary states: a cold, cloudy, dust-free climate (like we've seen over the past year) dominates when the planet is at its farthest from the Sun, while a warmer, dustier climate dominates when the planet is closer to the Sun. Some additional explanatory text is attached below, and the images can be seen at the URL:

http://oposite.stsci.edu/pubinfo/PR/97/15.html

Also, please note that the next series of Hubble Space Telescope observations of Mars will be obtained on June 4 and between June 26 to 29 (the exact dates and times are yet to be determined). These observations are the beginning of an extensive set of images designed to provide crucial support for the Mars Pathfinder landing on July 4th. As always, supporting groundbased visual observations, photographs, drawings, or CCD images of Mars shortly before, during, and shortly after this time period could be extremely helpful in interpreting the HST data. If you are able to obtain observations, please email your results or upload them using the instructions at the URL:

http://mpfwww.jpl.nasa.gov/mpf/marswatch_ftp.html

As of this writing, hundreds and hundreds of amateurs and professionals have uploaded spectacular photographs, drawings, CCD images, and even videos of Mars as viewed during 1996-97. Images from September 1996 through May 1997 can be viewed and downloaded from this JPL-based archive. My informal survey of the archive shows that there are extended time periods when Mars was imaged every day for many days in a row, or multiple times per day from different locations. Data have arrived from all over the U.S. and from many observers in Canada, Europe, South America, and Asia. This has been a truly spectacular success in terms of internation amateur-professional collaboration! Please visit the archive and feel free to download some of these spectacular views of the Red Planet! The URL is:

http://mpfwww.jpl.nasa.gov/mpf/marswatch_images.html

We would like to announce that a workshop of Mars telescopic observers and spacecraft remote sensing scientists is being planned for October in Tucson Arizona. The workshop will be a small, focused gathering of amateur and professional Mars researchers, organized by Dr. Ann Sprague of the Lunar and Planetary Laboratory and sponsored by the Lunar and Planetary Institute in Houston. Anyone interested in attending or presenting some of their results should read the attached information below and get your name and address put onto the mailing list for future notifications.

We regret to report that Leonard Martin, a long time member of the planetary sciences community, passed away suddenly and unexpectedly on April 7.

Just as Lowell Observatory is instinctively associated with the study of Mars, over the last two decades Mars research at Lowell was synonymous with Leonard Martin. Leonard began his observational career in the International Planetary Patrol, a globe-circling network of observatories which provided continuous photographic monitoring of Mars near its oppositions. During the late 1970's, Leonard coordinated ground based observations with several Viking global imaging sequences, revealing detailed structures for clouds and albedo features detected telescopically. As interest in Mars waned following Viking, Leonard was able to preserve Lowell's photographic record of Mars oppositions with the support of the National Geographic Society and continued the series of airbrushed albedo maps produced in collaboration with USGS. For the last several oppositions Leonard directed a series of multispectral CCD observations at Lowell Observatory, the most recent of which were obtained in February.

Although Leonard was a firm believer in the value of the historical record in providing a context for interpretation of spacecraft images, he always emphasized the temporal and geographical limitations and biases of telescopic as well as spacecraft data. He liked to have time to savor and assimilate new observations and was happiest professionally when he was pouring over Viking images or sets of telescopic photos. Such activities led at one time to his discovery of an unexpected group of dust storms in Echus Chasma and, later, to his careful compilation of the historical record of dust activity on Mars. Since 1990 Leonard was heavily involved in Hubble Space Telescope Mars observations and contributed to several discoveries based on the WFPC images. Leonard's many papers based on the photographic record revealed to many of us (whose impressions of Mars were derived mainly from spacecraft images) that the planet is a changing, dynamic system and that observations of a small group of years, however detailed, did not reveal its entire nature. His quiet, but persistent voice lent a tone of reality to many "Mars debates," and his contributions invariably helped to advance our understanding of Mars. His encouragement and mentoring of younger colleagues started many of us on our way to careers in Mars research.

Leonard Martin finally was forced to surrender his active role at Lowell Observatory early this year because of health problems. He and his wife, Claudia, moved to Bend, Oregon, where the elevation and climate would be more beneficial to his health and he would still be able to participate in his favorite avocation, skiing. He was not giving up on active participation in HST and other programs, however, and was in the process of establishing Internet connectivity in Bend in order to preserve his active participation in Mars research.

His familiarity with diverse groups of Mars data was unmatched, and his role in the community will not be easily filled. He was the last of a prestigious chain of telescopic observers of Mars at Lowell, and "his like will not soon be seen again." Leonard Martin will be deeply missed by all of us who were privileged to know and work with him.

(tribute written by Phil James, Jim Bell, Todd Clancy, and Steve Lee)

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MARS' CHAOTIC CLIMATE

If you think the weather on Earth is unpredictable, try living on Mars. One week, the sky is pink and cloudless, filled with windblown dust raised from the rusty Martian surface. By Martian standards, it's warm, about minus 40 degrees Fahrenheit. Then, in a matter of days, the dust is swept from the atmosphere, temperatures plummet 40 degrees, and brilliant water ice clouds appear against a dark blue sky.

Dramatic weather changes like these may not seem very different from a batch of severe thunderstorms passing through your home town, but for Mars these changes can sweep over the entire planet every week. It appears that Mars' roller coaster-like weather is more chaotic and unpredictable than scientists first thought. Observations by the Hubble Space Telescope and the National Radio Astronomy Observatory (NRAO) radio telescope at Kitt Peak, Ariz., show that the atmosphere of Mars is more complex and variable than the picture revealed by the Viking and Mariner 9 orbiters. These spacecraft collected information from the planet in the 1970's and painted a fairly one-dimensional picture of Mars' climate. Images snapped by the orbiters revealed huge dust storms spreading throughout the entire atmosphere when Mars was closest to the sun (perihelion). These dusty conditions continued to dominate the planet's climate when it was farthest from the sun (aphelion). (Perihelion and aphelion occur every Mars year, which equals two Earth years. Aphelion occurs in northern summer, perihelion in southern summer.)

But information captured by Hubble and NRAO show that Mars is more often cloudy than dusty, experiencing abrupt planet-wide swings between dusty and hot and cloudy and cold. A state of emergency would be declared on Earth if an ice or dust storm blanketed the entire planet.

These shifts in climate are driven by three important factors: Mars' thin atmosphere, its elliptical orbit around the sun, and strong climatic interactions between dust and water ice clouds in the atmosphere. Mars' atmosphere is so thin that it weighs less than 1 percent of Earth's atmosphere. Because Mars' atmosphere is so paper-thin and there are no oceans to store up heat from the sun, the planet's temperatures respond more quickly and intensely to surface changes and atmospheric heating by the sun. There are also much larger annual changes in sunlight falling on Mars than on Earth, because Mars' distance from the sun varies by 20 percent in its orbit around the sun every two years.

Mars' elliptical orbit leads to planet-wide changes in atmospheric and surface temperatures over the course of a Mars year. During perihelion, when Mars is closest to the sun (summer in the southern hemisphere), the planet receives 40 percent more sunlight than during aphelion, when it is farthest from the sun (summer in the northern hemisphere). This annual variation in sunlight causes 35-degree Fahrenheit increases during southern summer (perihelion), forcing continental-scale dust storms at the planet's surface. The dust is swept aloft to altitudes of tens of miles, where it spreads globally, absorbs light from the sun, and heats the entire atmosphere by another 30 to 50 degrees Fahrenheit. This dusty perihelion climate was observed by Viking and Mariner 9 and by NRAO in 1992, 1994, and 1996.

But what the 1970's orbiters did not identify was the very distinctive Mars aphelion climate, with its planet-wide belts of water ice clouds. These clouds are as striking as the perihelion global dust storms. During the aphelion climate, surface dust raised by low dust storms is confined to low altitudes (about 10 km or 6 miles), and is eventually swept to the ground by water ice clouds. These clouds surround the planet at altitudes of 3 to 10 km (2 to 6 miles). It is the cold atmospheric conditions of Mars during aphelion, when the sun is much weaker, that stimulate the formation of these water ice clouds. The clouds further reduce atmospheric temperatures by forming around the dust. Without sunlight, the dust freezes and falls to the ground. This strong competition between dust heating and cloud cooling drives sweeping annual and short-term regional changes in Mars' climate.

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To: Mars Observing Community
From: Jim Bell, Ann Sprague
Re: Second Synodic Mars Telescopic Observing Workshop

May 15, 1997

Mars Telescopic Workshop 2:

The second Mars Telescopic Workshop is planned for October 2-3, 1997 at the Starr Pass in the Tucson Mtn. foothills. This gathering of professional and amateur Mars observers will be similar to the successful 1995 Mars Telescopic Observations Workshop held in Ithaca, NY. There are many important goals for the meeting:

* This workshop will provide the first opportunity for Mars telescopic observers to synthesize the results gleaned from the 1996-97 apparition with the results recently obtained from the Pathfinder primary mission (to be completed in August).

* It will also provide a chance to review synergistic Pathfinder and ground-based observations and bring together observers and mission scientists for useful discussion a structured yet informal setting. * The meeting will provide the opportunity for the Earth-based community to provide a consensus determination of the "state of Mars" prior to the global mapping by the Mars Global Surveyor mission that will commence in early 1998. This includes dust opacity, water vapor history, cloud activity, and surface composition.

* We can continue to explore the theme of short-term climate change by comparing the results from the 1996-97 (and 1994-95) aphelic apparitions with those from earlier groundbased and spacecraft measurements. Specifically, what is the history of dust and atmospheric volatiles during the past few Mars years examined, and how do these compare with Viking-era data?

* We can continue to forge important links between the professional and amateur/educational communities by allowing these groups to interact in a small, focused environment. I think this worked well in Ithaca in 1995.

* As a community, we should work to continually revise the consensus view of the role of continued groundbased observations, in light of the most recent spacecraft discoveries and also in light of constantly-evolving detector and telescope technology.

The program committee will select oral presentations based upon abstracts submitted with the registration forms. Participants are encouraged to submit abstracts on the following topics:

1) Ground-based (both professional and amateur) and HST observations of Mars' surface or atmosphere. Observations should be synergistic to or augment planned and future Mars spacecraft experiments.

2) Science experiments planned for Pathfinder, Mars Global Surveyor or other future Mars Missions that will be enhanced by ground-based or HST telescopic observations.

There will be informal field trips to local mountain top observatories scheduled for Saturday October 4, on a first-come-first-sign-up basis:

a. Kitt Peak (Space Watch, 4 m etc.), b. Mt. Hopkins (New Technology etc.) c. Mt. Bigelow (Kuiper designed 61 inch planetary telescope) d. Mt. Lemmon (several small facilities including lunar coronagraph)

For more information and to receive future mailings about the workshop, please send email to Jim Bell or Ann Sprague (addresses below) and provide us with your surface mailing address. An initial mailing and registration forms will be sent to you by the Lunar and Planetary Institute.

Conveners:
Ann Sprague, University of Arizona (sprague@lpl.arizona.edu)
Jim Bell, Cornell University (jimbo@marswatch.tn.cornell.edu)

Sponsors:
Lunar and Planetary Institute
University of Arizona
Cornell University