A Traveler's Guide To Mars
Interview with Bill Hartmann
Astrobiology Magazine (AM): The introduction to your Traveler's Guide mentions a potential readership of 'armchair explorers the world over'. There is an 'armchair' project for the public to point the orbiting camera on one of the current survey missions. What is your opinion of how the public can now suggest such target photos for the Mars Orbital Camera , and their first selection list , which would seem to feature polar ice and Olympus Mons, among other targets? Surprising or predictable, based on the images you and your students have poured over in detail?
On the other hand we have to be careful of the growing syndrome in education to "avoid textbook learning" (I've heard educators say that!) and just "engage the students" and keep them entertained. What I mean is that I hope teachers will go beyond the "hands-on activities" so dear to current education, such as helping to target images or engage in Mars rover exercises -- and transmit also the fundamental underlying science questions that we as human beings are trying to answer...and then discuss the fundamental (17th, 18th, 19th century) science principles that lie behind answering those questions!
AM: In your book, you tell the story of one instance in which a camera pointing task became a personal challenge. You tried to get the Mars Orbital Camera pointed obliquely across the largest volcano in the solar system, Olympic Mons, as an astronaut might view it. Since capturing this image was initially greeted as not as 'scientific' as the high-resolution, straight-down shots, would that picture still be your favorite if asked to submit another target like that today?
BH: There are a number of regions I'd like to see photographed in that "human" oblique view angle, the way we are used to seeing the land from our airplane windows. My favorite past picture or future target from MSG/MOC or from Mars Odyssey seems to change from month to month, I guess depending on current science results and personal enthusiasms. As I tried to describe in the book, I don't regard the oblique shots as unscientific at all, because I think that they inspire a broader, more holistic view that lets us see Mars in the context of our terrestrial experience (not as an alien "target"), and that in turn inspires new thinking, a new sense of relationships, and new questions. The argument against them at the time was that they would be no higher resolution than other images (whereas straight down gives very high resolution from MGS/MOC). But now that argument would obviate all Mars Odyssey images, since Mars Odyssey is lower resolution than Mars Global Surveyor images! That would be silly. Each type of image has its own role.
I'd love to see obliques looking down Valles Marineris, across some of the big frosty craters, across some of the lava flows, down big riverbed channels like Ares Vallis and Ma'adim Vallis, and so on. The problem is that we had only a narrow window of opportunity, when MGS was in its initial high orbit. Now it is lower, and moves so fast that an oblique image is very distorted while it is scanned, due to spacecraft motion during the exposure.
BH: I think an historic opportunity has been lost forever. When the USSR collapsed, the Russians and Americans had a beautifully complementary set of capabilities that could have been joined to promote human space exploration. They had a functioning MIR space station, cheap human transport to orbit, and much larger boosters than we did. We had high technology, miniaturized components, a workhorse shuttle, and lunar landing experience. We could have had some exciting joint programs that would be a role model for future space development. But while there were some who saw that vision, there were powerful factions in Washington who were opposed to any real collaboration. I talked to one Republican Senator who said the underlying objective in the 90s was to be sure Russians never again had a strong aviation/space capability, and therefore America should avoid any collaboration. On another occasion, when I was on a major policy review panel after Challenger, a colleague and I proposed 'win-win' use of the Russian Proton boosters to support US missions, and this was ruled as a totally unsellable idea in Washington and taken "off the table" as a permissible topic of discussion.
The Russian space teams hung on thru the Mars 96 mission, which would have been an incredible success if only one-third of the instruments worked -- but when it failed on launch and ended up in the Pacific, the Russian economy was tanking, and it was the death knell of an effective program of major Russian missions that might have capitalized on the Soviet-era technological investment.
AM: In your book's introduction, the Russian academician Mikhail Marov's answers the question of 'Why Mars?' in a couple of ways. His answers range over four possibilities: Mars' interesting water history, its potential biology, its model for understanding terrestrial climate by comparison, and finally the interplanetary adventure itself. Which one do you class as the top choice in the current round of 2003-2004 missions? The current Mars motto seems to be 'follow the water'.
BH: Martian water, climate, and potential biology are all tied together, and you can hardly investigate any one of the three without 'willy nilly' working on the others. We think liquid water is important for life, and whether liquid water was at a given place at a given time depends on the climate cycles (esp. the 15-million year cycles of axial tilt change, which led to frost and ice deposition at different latitudes in recent geologic history. And, as I've been saying in my public talks, the question of whether life formed on Mars is a perfect scientific question because either answer is so profound. If yes, it means we aren't alone in the universe. If no, then we may alone than we thought, and something might be wrong with our ideas of life's origins.
Underlying it all is the importance of establishing a human capability to operate throughout the inner solar system, and learn how to utilize the 24 hr/day free solar energy and asteroid resources -- and that ties into the general theme of adventure, i.e. fundamental exploration.
AM: Your Traveler's Guide is packed with visual inspiration, ranging from the early hand drawings from 19th century astronomers to the orbiting cameras to finally the surface shots from Mars landers. One point you make is how deceptive some of the early telescopes proved to be, since hand-sketching of fictitious features like canals set back later astronomers trying to view Mars with fresh eyes. It gave a picture of Mars as a blue-green oasis for writers, painters and scientists. But based on that same kind of a bluish-green mirage for life on Mars, eventually those fake canals ironically inspired the whole science fiction genre -- like HG Wells, Edgar Rice Burroughs, and Ray Bradbury-- even up to the early 1950's. As an artist and a scientist, what imagined painting or landscape would you most want to do next yourself, based even on one yet untaken image from the current landing blitz and their up-close shots?
On my easel I have a newly started painting of the light filtering through a Martian dust storm. And I'm partial to an image I have in mind, of the loneliness of our plucky landers -- not a lander closeup, but the lander or rover sitting out there in the middle of nowhere, all by itself.
AM: Matt Golombek, JPL's Pathfinder Project Scientist, has commented elsewhere that when the first landing site pictures are transmitted, the mission scientists will be able to gauge a majority of the geology quickly from that first panorama--for instance, whether it is rock spillage and geology likely associated with an ancient outflow or river. There is also some history with the first Viking image having a miscalibration on the sky, because modellers considered a faint blue sky possible, but later that color was better represented with faint pink. Overall, how do scientists plan a ninety-day surface mission, when so much seems to be riding on the first of thousands of eventual pictures?
BH: I think the first pictures are crucial only in the sense of getting the imaging system calibrated. That amusing mistake with the first Viking 1 pictures -- releasing an image with a blue sky -- really was an example of what we didn't know and why we went there and what we were learning! The problem I see now is the feedback between public and media, which emphasizes only the first pictures. The first ones get on nightly news and front pages, then the mainstream media pack it in and go to the next "media sensation." What we really need is for the public to demand more news in the second week and the sixth month, when the cameras are beautifully calibrated and the really exciting results are coming in -- and the media are talking about Madonna or the latest shooting.
AM: To help amateur astronomers with backyard telescopes, is it fair to say that the darker regions on a global view of Mars are newer geologically (fresh dark lava basalts) and the lighter regions are finer, weathered dust and thus older? How does this broad view differ for those who study the dark regions on the moon, since it's kind of the opposite there. The effects of wind and the martian atmosphere have such differing influences than strictly crater impacts
BH: In general its been shown that the bright areas [on Mars] are rich in fine, oxidized dust, and the darker areas seem to have coarser materials -- though not massive EXPOSED outcrops of rock. Dust and gravel covers everything to some extent. On the other hand (I've always been intrigued by this) why do the dark markings stay dark?
The whole story can't just be windblown dust, or materials would have been mixed to a uniform brown. Probably the dark markings tend to contain more localized outcrops as sources of fresh rock gravels and sands. Syrtis Major, the most prominent dark marking, for example, is centered on a large, old volcano where fresh basaltic lavas may be eroding and producing dark soils. Controlled by prevailing winds, the movements of these materials deposit different materials in different areas.
It's fascinating to study Mars with a small telescope and sketch those markings, and realize how complex nature can be in creating patterns visible from a back yard part way across the solar system!
AM: All the current missions are targeting more equatorial regions of the northern hemisphere this time, mainly because of its seasonally longer days and extended power from solar collectors during the surface operations. If the planetary scientists could choose (in splendid isolation from all engineering considerations), do you think there would be more polar missions and a few more to the south? Are there reasons to suppose either the hydrology (or even potential biology) might be richer hunting if a lander was off the equator or in more rugged terrain?
BH: Definitely the underground ice is closer to the surface, the further you go from the equator toward the poles. One piece of evidence is the mud-like ejecta from shallow craters at high latitudes, and another piece of the puzzle is patterned ground, as observed in tundra regions of Earth. Icy soils give at least the potential for moist soils and life-nurturing environments. If you land near the pole in summer, you may sit on ice or have the ice within a foot or two of the surface, as shown by Mars Odyssey findings. And remember, such a site can have 24 hours/day of sunlight in summer, a bit weaker than at equator, but available all day long to charge the [solar] batteries. (By coincidence, Mars has about a 24 hour day like Earth).
As a result of these ideas the Phoenix mission, now being built, will land near the pole and scratch the ground to look for signs of life in the ice-rich soils.
BH: One of the most intriguing and little-discussed aspects of this rock is that it is that out of 28 rocks from 4 to 8 impact sites on Mars, it is the only one older than 1300 million years! 27 out of 28 are from the last 1/3 of Martian time. This suggests that the older parts of Mars rarely launch meteorites. Why?
Impact studies, as summarized for example by Arizona researcher Jay Mulish, indicate that the best launch conditions are solid, coherent rock within top 50 meters of surface -- for example young lava flows. Martian areas older than 1300 million years are typically eroded and beat up by impacts. The resulting loose, porous, "megaregolith" was probably the idea sink for Martian water and may be full of ice.
So impacts into the older regions of Mars probably produce a blast of dust and steam, and few rocks launched into space.
This brings us back to Allen Hills 84001. It's 4500 million years old, a piece of the original crust! So how did it get launched. There is a fascinating clue buried here! It seems to mean that regions of the original crust, formed 4500 million years ago, are actually exposed on Mars. What's exciting about that is that it isn't true for Earth or Moon or maybe any other planet.
Earth's original crust was long ago destroyed by plate tectonics, mountain building, subduction, etc. The moon's is buried under a mile or two of megaregolith and inaccessible to impact or observation. So Mars may be the only planet where we can land and walk around on the primordial crust, and pick up samples for geologic analysis, to learn how planet surfaces formed in the first place!
AM: You describe a rather fascinating, but discouraging, letter you got as a graduate student from Nobel Laureate Harold Urey, who also did the early biosynthesis work in the now famous Urey-Miller experiments. He had a long feud with your supervisor, Gerard Kuiper, who also has the Kuiper Belt region beyond Pluto named after him. This seemed a battle of titans. Urey's hasty criticism of your paper centered on the concentric geometry of crater impacts on the moon. Can you comment today on some of the more remarkable martian examples of these rings around craters, ranging from how important it may be to determining the depth subsurface ice to the Inca City mystery of a partial ring that is weathered in a peculiar cracking pattern?
BH: As shown by MGS camera builders Mike Malin and Ken Edgett, the "Inca City" structure is indeed part of a ring system around an old impact. But the classic sorts of bullseye-shaped, multiple concentric ring systems found around lunar impact basins (and impacts on Mercury and even Ganymede and Callisto) are hard to see on Mars. Most large basins formed in the first 1000 million years of planetary history, and on Mars such old features are highly eroded, covered, and cut up by river channels, deposition, lava flows, etc. (On Earth they are gone entirely, due to erosion and plate tectonics).
When I look at the rim structures of old Martian basins, it seems to me that the rims may have formed from loose, piled up ejecta, blown out of the basin and piled on the rim. If so, they have have been some of the easiest materials to erode by wind and water. In the case of the giant Hellas and Argyre basins, it almost seems that the main inner rim is completely dissected and eroded, but by river channels and transformed from a high continuous rim to a remnant maze of low hills.
BH: I think the mania for "neutral" and often "cute" names is beginning to be more destructive than helpful. As my archaeologist wife commented recently, the appealing story about Mars is that it is so Earth-like, but the proliferation of strange sounding geologic names for surface textures, like "chaotic terrain," "fretted terrain," and so on, leads the public to perceive Mars as ever more alien and non-understandable.
These names come from an important geologic tradition, that you must first describe in neutral terms (implying no hint of actual hypothetical process), and THEN interpret. This was started with a vengeance during the the Mariner 9 imaging team interpretations in the early 1970s, in which I was involved. But its gotten out of hand! I've heard entire scientific papers at meetings, which consisted merely of "translating" a spacecraft image into jargon to describe terrain types -- "cantaloupe terrain," overlain by "basketball terrain", abutted by "pitted terrain", cut by "grooved terrain." At the end of the paper you, the audience, truly knows exactly nothing than the information that was visible in the initial image!
Not to mention the 25 year absurdity of the "face on Mars," a whimsical name that got completely out of control, with the "face on Mars" buffs claiming NASA purposely aborted the Mars Observer mission to hide the truth, and later requiring our Mars Global Surveyor team to drop its science plan, reorient the spacecraft, and waste tax dollars to get images of the "face" as one of the first activities of the mission. The pictures would have come in a few months later as the spacecraft routine started taking pictures of that region, but, no, orders came down from NASA Headquarter that we had to do it now, because the public (i.e. a few tabloids and sleaze TV producers) wanted to know -- and we got our nice pictures of the boulder-strewn, mesa-eroded dirtpile. And the tabloids and sleaze TV producers have moved on to something else.
BH: The lack of spectral detection of lakebed salts and carbonates does not prove that lakes never formed (as widely reported in the press) but only that if they did form, say 3 billion years ago, they are now covered and hidden by sediments and dust drifts.
Olivine has been detected spectrally in a few regions, and part of the dominant basaltic rock type, and it's true geologically that prolonged water exposure weathers basalt to other forms. So it's been argued that Mars was never very wet.
But on the other hand, it's just not true that this rules out water activity. Most Mars meteorites, studied in labs on earth, have clear evidence of having been exposed to moisture and salty water. One (named Lafayette) has enough weathered minerals that they could be dated by two labs (California and Arizona) and the water exposure was found to have happened 670 million years ago.
It's not a question of "never any flowing water on Mars," but rather a question of dates of water, duration of exposure of the rock and soils to water, replacement by fresh unweathered rocks such as lavas. After all, earth has lots of basalt rich lava flows and even whole beaches of olivine rich sand with wave lapping on them (I've walked on them!). And no one is going to characterize Earth as a planet devoid of flowing water!
AM: Any thoughts on the biology experiments to be done on Beagle 2, to revisit the Viking suite which looked for soil metabolism?
BH: The biggest problem is that most mars mappers assign the probable period of abundant lakes to the Noachian (early) or Hesperian (middle period)-- they would be surfaces perhaps 3000 million years old or older. But in that time, such a surface gets beaten up and pulverized to depths of a meter or so by impacts (as we found on the moon, and as I showed in a recent paper in Icarus), in spite of the fact that the smallest meteoroids (< few cm in size) get broken up in Mars atmosphere. If you had a deposit of 1 inch of pure salt on it, that deposit would have been ground up, mixed, and probably blown away by now.
So...a nice 3500-million-year-old lakebed deposit full of diagnostic minerals and hypothetical fossils has been pulverized and plowed by impact, and possibly dispersed, not to mention probably covered by windblown dust and sand deposits. So the big challenge is to be lucky enough to set down an an ancient lakebed that has been preserved.
My favorite site from that point of view is the hematite-rich area in Terra Meridiani, because I can see some signs from the cratering record that it may have been covered over, preserved, and only recently exhumed (as I described in the same article in Icarus a couple of years ago). So it's my favorite candidate for a preserved ancient surface with possible hydrothermal water modification that helped create the hematite.
AM: Where will you be during the mission coverage? Glued to TV coverage, or following it on the internet, or on vacation in the Tuscon desert with your paint brushes?
But, in an odd way I've started trying to organize my head so as not to attach so much importance to the "firsts:" the thrill of landing, the first touchdown, the first pictures. We are so much of a thrill seeking society that it interferes with a positive life; we want that little adrenalin rush, to the extent that we lose interest in things later, when there is no "exciting first." Go to airports and you see a lot of people who can't stand it if they are "stuck" somewhere where nothing is happening and they don't have their infrastructure of machines and sports to keep them entertained (hence junk TV and cell phone addiction).
Part of problem for science and exploration is that everyone wants to feel the thrill of being there at beginning, but that very syndrome makes public and media lose interest after day one. As I mention in the book, in early days much of the media used to go home from JPL after the first pictures came in from a mission, and editors regarded 3rd or 4th day Viking lander pictures as "old news" -- which meant that the public was deprived of the best images after the technicians really got the cameras working well in color! Even now only the first day pictures show up on the mainstream news media, and you have to seek out special web sites for "junkies" who want to keep up on the story.
I'm for "spreading the thrill out over time," maintaining a sense of wonder as the later (usually better) pictures come in and the data begin to solidify from a mass of confusing facts into a real story about Mars!
The Real Story comes six months later!