Yes, I believe that's true, tty.

Interestingly, though, the PDF version of this particular paper wasn't available for several days last week on the Science website, though the full text HTML version was. I haven't checked since then to see if the problem was fixed.

Here is another site (scroll down to the bottom of the page) that has the PDF version of the Malin and Edgett paper, as well as a rare PDF version of the accompanying Perspectives piece by Ken Tanaka.

Re dormancy: If hypothetical Martian bugs can survive extended freeze-drying, then they should have been distributed globally by the wind long ago. Maybe we just need to land an ultra-sterile nutrient solution with an automated microscope pretty much anywhere, toss in some soil, and see what grows...

Even negative results would be most informative. If sporulated bacteria aren't all over the place waiting for water (or dilute H2SO4?) to wake up, then that would set some significant constraints on Mars' biological history--if there ever has been any.

Would those nutrients consist of nitrates or sulfates? or perhaps silicates? That was one of the things that made me scratch my head over the Viking experiment. How do we know our "nutrients" weren't a sterilizing agent? (I know, I know, you have to start somewhere.)

If the $$$s were there, why not have several different mixes & maybe just a distilled water-only vial as a control? Come to that, if the postulated critters were REALLY efficient, maybe the water is all they'd need; they'd eat whatever they usually do in the soil itself.

Now, light exposure is a whole other problem. Might want to do full dark, low-UV visible, and high-UV conditions (saving the high-UV for last).

I'm not sure this has been mentioned elsewhere in UMSF, and if it has, I apologize for the repeat; however, the June 2006 issue of Elements: An International Magazine of Mineralogy, Geochemistry, and Petrology is a special issue entitled "Water on Mars."

(Download entire issue - 11.3 Mb PDF)

For those who are interested, David Catling of the University of Washington has an article, "Atmospheric Evolution of Mars" (2.1 Mb PDF preprint), which is in press with Encyclopedia of Paleoclimatology and Ancient Environments.

I would have to think it would depend on the numbers. If habitability comes down to a few hectares per minute per year, I think even Good Ol' Durable Life would have a problem spreading enough bugs from one outburst site, spread planetwide, to have a prayer of any of them dropping into another eventual outburst site.

Another problem is that bacteria tend to take time to divide, whereas we haven't seen yet that anyplace would actually be wet for more than minutes. (Or at all, to be a stickler.)

This reminds me of a problem for possible bugs in the clouds of giant planets. There may always be a zone that is wet with comfortable temperatures, but any given bug would get swept down to sterilizing heat in typical situations. In the martian case, the bacteria thriving at one outburst site would have to be so numerous that a tiny fraction of them would land in friendly environments. It's sort of like the math of a nuclear chain-reaction... in reverse.

And of course, airborne dust isn't a great place to hide from UV radiation.

It seems more likely that something would sustain itself locally than to live and travel in the global dustbowl.

It's amusing that both possibilities make some sense.

It will depend, of course, on the frequency and predictability of the outbursts. If there are a million possible gully locations but only 1000 of them will gush per century and we can't predict which ones will go next, then the 1/1000 stab in the dark with landers-in-waiting would not be remotely cost-effective. It's easier to imagine that cheap surveying could be done from orbit.

On the other hand, if the events turn out to be somewhat or highly predictable as to location and time then anything goes.

It has to be a priority to start to characterize the events' patterns of occurrence.

A problem would be if every gully site only gushed *n* times, exhausting a finite reservoir of ice. If so, then the places where gullies have already shown themselves could be the places where there are least likely to be new ones.

Actually, a combination of the two ideas might make the most sense. Assuming multiple probes/landers/penetrators could be carried, land a few at carefully selected, predetermined sites, and then hold one or two in orbit to exploit any "fresh" sites.

Special Coverage: Liquid Water and New Craters Discovered on the Surface of Mars
Planetary Radio
December 11, 2006

Thanks. I forgot to check that out. There were several papers being discussed, and I didn't make it clear which one I was talking about. I was trying to get the latest paper titled "Present-Day Impact Cratering Rate and Contemporary Gully Activity on Mars." Thanks to a philanthropic donor, I now have that.

The search for life on Mars is a tricky problem. We are only very recently learning what Mars is really like. It seems quite possible that any microbes launched onto the surface environment might be toasted, but life is a resilient and robust thing. Life has managed to evolve quite a number of mechanisms to deal with challenging environments on Earth. Who yet knows what it is capable of elsewhere.

Assuming it can not survive on the surface of Mars, we might need to capture it as it is expelled from a more benign, subsurface environment. Drilling down to a wet reservoir seems to be a hit-or-miss proposition unless we can accurately identify and rove to the correct locations. Yes, there are more frigid places near the outer planets where liquid water may exist, but Mars is where we need to do more exploration.

FYI, I made a change to a post earlier in this thread.

I was "shoked" by M.Malin's assesment of the high probability of having a crater formed in your viscinity if you stay 20 years at the same spot. So, now, I wonder of the probabilty that a meteroid hit a "gully" zone and/or hit close enough that the effect will be to activate some gullies. Has this been already addressed or the probabilities are too remote to be considered?

It's rare that I reference another board but I recommend reading Jon Clarke's posts on this topic on the Space.com Message Boards (Space Science & Astronomy Forum), starting with this post. Some might note Jon occasionally posts here, too. "borman" also has some interesting posts in that thread.

Of course, I'd also recommend that you completely disregard some of the others

I haven't read or heard anyone make a connection, direct or indirect, with impact events and gully activity, though some sort of seismic activity triggering the outbursts is very plausible.

For some discussion on "alternate" theories of the gullies' formation, take this trip down nostalgia memory lane.

But that wouldn't address the apparent issues of disparity between sunward/shadeward facing slopes.

Andy

You're rigth Andy. Unless there's a very (improbable) narrow equilbrium. Would be important to know if brusts-gullies occure anytime during the year or more like the "geysers" at particular time of the year. Only a dedicated orbiter could address this. I wonder if there are other interests of having a regular picture (every 2 weeks) of Mars other than addressing the gullies formation. Up to last week, before the announcement, I didn't read about such a project, except for meteorological purposes. I forsee polar caps behaviour to add, landers relay, what else?

That's true, AndyG. And I should have been more precise in my reply. What I was driving at was that with only two apparent examples of recent (ca. 7 years) activity among the "thousands" of gullies, a non-insolation trigger might be plausible. I'm assuming, of course, that the putative near-surface reservoirs of liquid water do not vary temporally and spatially.

Hecht and Vasavada have a new paper, "Transient liquid water near an artificial heat source on Mars," which was just published online in the open-access MARS Journal.

My long-standing suggestion here is that the sun-facing slopes don't form gullies because they would have already exhausted their reservoirs long ago, like short-period comets.

In a nutshell, a gully can form when a slope experiences something close to a meteorological record high temperature plus other factors (a little more dustpack on top of the crater) add enough stress to break the camel's back.

Seismic activity would have to be particularly well timed to have an effect.

Note that certain fault systems on Earth are more likely to experience a seismic event depending upon the tides. But obviously the overwhelming majority of tidal events (every 13 hours) do not cause quakes. It just becomes the straw that (rarely) breaks the camel's back.

Frozen rivers (such as the Nenena) break every spring when the ice melts. Presumably, a stick of dynamite well-placed on the day the ice was going to break anyway could speed the event by minutes or hours. But a stick of dynamite would not possibly cause it to break (riverwide) in January.

An exogenic trigger for seismic activity (e.g., impact-induced) would, I agree, suffer from the dreaded "Tooth Fairy" hurdle, which I mentioned in another context.

However, it's not too much of a stretch to posit that endogenic seismic activity, assuming it occurs on Mars, could trigger outbursts. And, again, the paucity of detectable activity among the tens of thousands of sites is not an insignificant issue.

There's something that make me scratch my head.
They're talking of ten of thousands gullies with only two changes in 6 years.
I can't imagine the "light tone" deposits stay for a very short period (< 6 years), so, why MGS didn't see light tone deposits at first, back in 1999?

Don't scratch...Think!
Maybe MGS catch a transition period?...
Don't you see the main bright flow getting darker and darker in a short years's period?
Mars is EX-TRE-ME-LY dynamic...

The Planetary Radio interview with Ken Edgett is now online.

Is it his accent, perhaps?

Bob Shaw

Here are a couple of new martian gullies-related papers in press with Icarus:

Martian gullies in the southern mid-latitudes of Mars: Evidence for climate-controlled formation of young fluvial features based upon local and global topography
Icarus, In Press, Accepted Manuscript, Available online 23 December 2006
James L. Dickson, James W. Head and Mikhail Kreslavsky
PDF (724 Kb) (Subscription required)

Comparison of small lunar landslides and martian gullies
Icarus, In Press, Corrected Proof, Available online 21 December 2006
Gwendolyn D. Bart
Abstract

For non-subscribers, click here for more information on Gwen Bart's work (scroll down for links to her martian gullies work, which was presented at LPSC earlier this year).

As for Dickson et al., you may also wish to keep an eye on the Brown University Planetary Geosciences Group publications page. I suspect the paper will be available there fairly soon.

I just noticed a new paper in press with Icarus:

Observations of Martian Gullies and Constraints on Potential Formation Mechanisms, Part II: The Northern Hemisphere
Icarus, In Press, Accepted Manuscript, Available online 3 January 2007
Jennifer L. Heldmann, Ella Carlsson, Henrik Johansson, Michael T. Mellon and Owen B. Toon
PDF (1253 K) (subscription required)

I believe this is a companion piece to an earlier paper in Icarus by Heldmann and Mellon [2004]. For those without access to Icarus, here is a (715 Kb PDF reprint).

By the way, in case anyone wants to wade through a master's thesis on this particular aspect of martian gullies research, see Nina Lanza's submission earlier this year in May 2006 to Wesleyan University: "Geometries of martian hillside gullies in the northern hemisphere: evidence for an insolation-driven mechanism of formation" (8.01 Mb PDF).

At first this topic included the discovery of recent craters and as I don't know other place to post this message, I post it here.
I didn't realise that, from MGS observations, the rate of formation is one crater per MONTH. Whoua, that's a lot. They also said that is you stay in the same place for 20 years, you'll be close to one impact. Vicking landers have been there for much longer. Does somebody know if the location of the fresh craters has been released?

Glad you mentioned this, Climber; been wondering about the implications for landing/settlement.

The big question seems to be whether the amount of risk incurred for surface installations on Mars is significantly above the Earth background level. Our atmosphere conveniently disposes of many otherwise dangerous meteors, but will we have to deeply bury any future Martian colonies?

I don't know that the impact rate is enough to cause huge problems for individually pressurized buildings and facilities. On Earth, there are several hundred lightning strikes per second, many of which occur close to buildings and people. And yet, while there is a certain amount of damage (mostly to trees) from lightning strikes every year, rather few people are injured or killed by lightning each year.

Now, compare the frequency of lightning strikes to the frequency of impacts on Mars, and factor in the percentage of those which are large enough (those that make craters of, say, 100m or more in size) to blast you even if they don't hit you directly, vs. those which create craters of only 10 or so meters or less in size (which could land 100 meters away and not damage your habitat), and I bet you're far less likely to get hit by a meteor, or have your domicile destroyed by a close impact, on Mars than it's likely you would get hit by lightning on Earth.

Also, look at the number of pieces of the space shuttle Columbia which fell onto a couple of towns in Texas. Out of all of those pieces, very few actually hit buildings, and *none* hit any human beings. Heck, I don't think there were any documented cases of any pieces hitting any animals, even. So, you can drop a good number of objects onto a fairly densely populated area without actually hitting anyone.

Now, I grant you, if you built big transparent pressure domes on Mars, you'd increase the probability of a meteor causing a depressurization event... but I'd bet you're not going to see anything beyond relatively small metal tubes in Martian colonial building styles for quite a while...

-the other Doug

Did anyone happen to listen to this Planetary Radio broadcast? I did and discovered a couple of things for first time during the Huntress interview:

1. MGS was the first spacecraft to use aerobraking, not Magellan.
2. THEMIS was an MGS payload and not, as I always suspected, on 2001 Mars Odyssey.

Yeah - I spotted that...I put it down to misscommunication between Wes and Matt.

Doug

Undoubtedly, and poor THEMIS. It and 2001 Mars Odyssey get no respect, except as a workhorse relay for MER. I remember when Christensen was a guest several weeks ago, when during the intro THEMIS was assigned to Mars Express (an error which was corrected in the next broadcast).

Aside from that, though, this latest broadcast and Huntress's whole discussion of water on Mars (and even the brief discussion of the new crater results) had a strange tilt to it, at least to me. I guess following Christensen and Edgett and their ultra-precise descriptions of the latest science results has its drawbacks.

Meteor strikes on Earth aren't unheard of.

http://astro.wsu.edu/worthey/astro/html/im...or/strikes.html

Mrs. Hodges apparently never completely recovered from being hit by one.

--Greg

I guess he considers Magellan aerobraking as a test, which, IIRC, it was at the origin since aerobraking was not used to get to primer orbit. May be not that accurate but far from the BBC's stuff.

I just noticed that a preprint of this paper is now available (2.5 Mb PDF).

FYI, the final version of this paper should be published online tomorrow in JGR-Planets.

Sorry to resurrect a long dormant thread but it seems like the best place to ask this question: In the planetary society blog Doug reported on a hypothesis that bacteria on mars could survive by using an intracellular fluid of water mixed with hydrogen peroxide. As an idea this makes some sense as at atmospheric pressure at least (I've not been able to locate a temperature-pressure curve for H2O2) a 60%-40% H2O2-H2O mix has a boiling point of 120 deg C and a freezing point of -50 degC. In other words its stable over nearly twice the temperature range of water. So (finally gets to the point) has it been considered anywhere that the liquid flowing down the gullies could be bleach? Google hasn't thrown up anything on the idea, although it has been convincingly argued that H2O2 could be produced in the martian atmosphere during storms and be coating the surface.

And at 6 mbar? That's the crucial point. You can mix all sorts of things with water to change the boiling point and freezing point - H2O2 is one of the more unpleasent ways of doing it - particularly on the UV soaked surface of Mars.

Doug

Not to mention the required quantities of H2O2 for the gullies. We'd be past talking about minute amounts but really significant quantities.

Both good objections! I suppose if the peroxide is produced during storms, and has been doing so for a long time it could have reached quite high concentrations in some regions, mixed in with soil and ice. As to the question of how it behaves at 6mbar thats up in the air (pardon my bad pun), I can't find anything on it. Theres no reason to supppose hydrogen peroxide over any other possible candidate, other than the argument for its production on mars has already been put foward in detail. Personally I'd favour H2O2, or something like, as 'antifreeze' for the gully water over salts ,which are frequently suggested, because it lowers the freezing point by an extra 30 degC, which would make high latitude polar gullies easier for me to accept as water related. I've not done any legwork on the idea, it just caught my imagination. I'll do some more digging and see if I can come up with some numbers.

If - and it's a very big if - there are appreciable quantities of H2O2 on Mars it could have important consequences for future exploration if it could be extracted. H2O2 at high concentration decomposes catalytically into H2O and O2 at fairly high temperatures. Imagine having a steam turbine that also produces water and oxygen!
H202 is even a fairly good rocket monopropellant as the germans demonstrated with Me163B.

Doug i appreciate that the 6 mbar point has been made, and made well with regard to liquid on the surface. However, i wonder how much depth of regolith/permafrost you need before the pressure of overlaying material allows H20, H202 etc to exist as a liquid? Is it 10s of meters or kilometers.

Do we have accurate modelling of the heat flow of hte martian crust to asses this?

Also proven by the American Mercury capsule spacecraft. Its reaction control system fuel was H2O2.

-the other Doug

No. One of the datasets that is most wanting about Mars is its crustal heat flow, both average and regional. Thermal emissions instruments (TES, infrared imagers, etc.) give a rough idea, but what I wouldn't give for a set of 20 or 30 heat flow probes scattered across Mars. I'd *almost* like that more than I'd like a seismic network.

-the other Doug

Well I couldn't find much on either the behavoir of hydrogen peroxide at ten mbar or less, or a copy of the paper on hydrogen peroxide snow theorized to form during dust storms that I could access. I suspect that these are moot points, as the martian soil is 20% iron sulfate, which a friend in the chemistry department assures me would cause H2O2 to decompose far to quickly for it to build up in significant amounts! So to answer my own question, no its not likely the gullies on mars flow with concentrated bleach!