More News From Mars? Afraid Nasa Funding Could Dry Up?

[Calilasseia]

One problem I can think of, that any Earth-origin bacteria would have to overcome quickly, is the interesting oxidising properties of Martian soil. Back in the 1970s, when the Viking missions landed, they performed what was then thought to be a reasonable analysis of Martian soil, and scientists got all excited when the initial results came back, which they thought was indicative of life having been present in the past, or possibly even in the present.

Unfortunately for those who got excited back then, it turned out that the Martian soil contains an abundance of perchlorate salts, which are vigorous oxidising agents. These would have some interesting effects upon the peptidoglycan molecules in Earth-origin bacteria, principally, oxidative breakdown followed by loss of cell contents. It's why perchlorates make good anti-bacterial bleaches.

On the other hand, the virtually anoxic atmosphere (92% carbon dioxide) would make life extremely hard for obligate aerobic bacteria.

So, the atmosphere would snuff out aerobically respiring Earth bacteria, and the soil perchlorates would destroy the cell walls of anaerobic bacteria even more quickly and efficiently than molecular oxygen gas. For example, Clostridium botulinum, the obligate anaerobic bacterium implicated in lethal food poisoning events, cannot reproduce if the surrounding medium contains more than 2% molecular oxygen, and only the resistant dormant spores would persist for any length of time under Martian conditions. It's possible that the perchlorate salts in Martian soil would pose a lethal oxidative threat even to the resistant spores.

Unless a bacterium happens to possess an extremely efficient superoxide dismutase enzyme as part of its biochemical machinery, it's probably not going to do well in Martian soil, unless it utilises perchlorates as a metabolite, such as the Firmicute rejoicing in the wonderful scientific name of Moorella perchloratireducens.

[Blind groper]

Good point, Cali.

I have to say, though, that it is unlikely that the perchlorate is in appreciable amounts everywhere on Mars. There are probably large areas where the amounts are too small to be an issue. After all, we have explored only a tiny fraction of the surface of Mars, and we know that Earth, at least, is not homogeneous, and it is unlikely that Mars is either.

[mistermack]

Good point, Cali.

I have to say, though, that it is unlikely that the perchlorate is in appreciable amounts everywhere on Mars. There are probably large areas where the amounts are too small to be an issue. After all, we have explored only a tiny fraction of the surface of Mars, and we know that Earth, at least, is not homogeneous, and it is unlikely that Mars is either.

It would be interesting to know what the core temperature of Mars is.
I know it's not as hot as Earth, because the vulcanism apparently stopped billions of years ago.
But if it's still warm, then there could be wet rocks below the permafrost, which could still harbour bacteria.

I think you'd have to dig down a long way for that, though.

[Calilasseia]

Mind you, scientists have found nematode worms living inside solid rock 3km below the surface. A paper covering this is this one:

Nematoda From The Terrestrial Deep Subsurface Of South Africa by G. Borgonie, A. García-Moyano, D. Litthauer, W. Bert, A. Bester, E. van Heerden, C. Möller, M. Erasmus & T. C. Onstott, Nature, 474: 79–82 (2nd June 2011) [Abstract available here]

Since its discovery over two decades ago, the deep subsurface biosphere has been considered to be the realm of single-cell organisms, extending over three kilometres into the Earth’s crust and comprising a significant fraction of the global biosphere1, 2, 3, 4. The constraints of temperature, energy, dioxygen and space seemed to preclude the possibility of more-complex, multicellular organisms from surviving at these depths. Here we report species of the phylum Nematoda that have been detected in or recovered from 0.9–3.6-kilometre-deep fracture water in the deep mines of South Africa but have not been detected in the mining water. These subsurface nematodes, including a new species, Halicephalobus mephisto, tolerate high temperature, reproduce asexually and preferentially feed upon subsurface bacteria. Carbon-14 data indicate that the fracture water in which the nematodes reside is 3,000–12,000-year-old palaeometeoric water. Our data suggest that nematodes should be found in other deep hypoxic settings where temperature permits, and that they may control the microbial population density by grazing on fracture surface biofilm patches. Our results expand the known metazoan biosphere and demonstrate that deep ecosystems are more complex than previously accepted. The discovery of multicellular life in the deep subsurface of the Earth also has important implications for the search for subsurface life on other planets in our Solar System.

[Calilasseia]

A pre-publication version of the full paper can be found here, by the way.

[Calilasseia]

I just found the full version ... here, complete with illustrations.

[mistermack]

I don't know much on the subject. But surely worms must be obtaining some oxygen from somewhere?
Don't animal cells rely on it for energy? They say "hypoxic conditions" but maybe these nematodes are just evolved to get by on a tiny amount of oxygen.

[Calilasseia]

From the paper:

Although Eukaryota, Bacteria and Archaea cohabitate in almost all surface environments on the Earth, very few searches for eukaryotes in the subsurface have been published. In South Carolina 0.1–10 eukaryotes per gram comprising algae, fungi, amoebae and flagellates have been discovered5 at a depth of 200 m, and in Sweden 0.01–1 fungal cells per millilitre, ,3 mm in size, have been found6 in 200–450-m deep fractures. In this study of the South African subsurface, we expanded the search for subsurface life to nematodes because they are one of the most successful metazoan phyla with respect to their abundances, distribution and physiological tolerance7,8; they can enter a state of anabiosis for extended periods; and they continue to metabolize aerobically in hypoxic environments where the partial pressure of oxygen (pO2) is only 0.4 kPa (ref. 9).

In short, they can survive in low oxygen environments, and if the going gets too tough for a while, they can drop into a suspended animation state.

From this article in Nature, we have this little reminder:

Yet their discovery is encouraging, even heartening, for it demonstrates, once again, that once life appears, it is hard to extinguish — and that there are few, if any, habitats in which living things might not survive, even thrive, no matter how seemingly unpromising the circumstances. Even today, when you may think that we have shaken every tree and looked under every stone on the planet, new creatures hove into view. It is rare, nowadays, to discover large vertebrates as yet unknown to science, yet such discoveries are still made.

Molecular methods have extended the reach of those formerly equipped only with traps and butterfly nets, allowing trawls of entire habitats for new forms of life — in the sea, in the upper air and even in the rich inner spaces of our guts. There is probably no slagheap too toxic, no nuclear-waste dump too radioactive, no smoking fumarole too fuming and no icy firn too frigid that it cannot be colonized by some enterprising microbe. A promise of a carbon source, a whisper of redox potential, and life will arrive. (Indeed, to encourage such endeavours, Nature promises a 500 g jar of Marmite to the research group that can identify the organism that digests this savoury spread. Tip: it is probably endemic in the intestines of Britons, to many of whom Marmite is an obsession, and absent in the more sensitive stomachs of Danes, who last week threatened to ban the comestible because of its evil added vitamins.)

Perhaps the habitats least explored and prospected for life are the most familiar: soil, sediments in ponds, and the seashore — the home of the meiofauna, creatures that make their living between particles of minerals and detritus. Meiofauna creatures at their largest are just at the verge of unaided visibility, down to about 40 micrometres in diameter — a world literally in the interstices, too small for every day, but too big to trouble micro- or molecular biologists. The meiofauna offer a community of tiny arthropods and a range of creatures otherwise encountered only in the dustier (and therefore most fascinating) pages of textbooks. This is the realm in which nematodes rule — and a kingdom to which we can now add, as Buchsbaum's unheralded scientist almost predicted, the ground deep, deep beneath our feet.

Indeed, the ubiquity of nematodes was recognised in a textbook as far back as 1914. The book in question being Nematodes And Their Relationships by Nathan Cobb. Someone kindly provided in the comments on that Nature page, the full quote from page 472 of Cobb's 1914 tome:

In short, if all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes, and oceans represented by a film of nematodes. The location of towns would be decipherable, since for every massing of human beings there would be a corresponding massing of certain nematodes. Trees would still stand in ghostly rows representing our streets and highways. The location of the various plants and animals would still be decipherable, and, had we sufficient knowledge, in many cases even their species could be determined by an examination of their erstwhile nematode parasites.

Oh, and of course, as well as nematodes, we have those wonderful creatures known as Tardigrades. Tardigrades are capable of entering a suspended animation state, that allows them to survive all manner of extreme conditions. Tardigrades have been demonstrated to survive for varying periods of time in environments such as the interior of an autoclave at 151°C. They can survive being frozen at temperatures as low as 1 Kelvin, they can survive in enhanced radiation environments, and workers preparing a sample of Tardigrades for electron microscopy were surprised to find that their specimens dusted themselves off and started walking about again after being examined under the electron microscope. To illustrate what a feat of survival this was, the specimens in question were dusted with Uranyl Acetate (an electron-scattering medium that in the world of electron microscopy, takes the place of more familiar stains used in light microscopy), a material that is sufficiently radioactive to require handling in a glove box. The specimens were them mounted on a copper grid, placed inside the electron microscope, subjected to a high vacuum (ambient pressure around 10-8 bar), then subject to being illuminated with a high energy beam of electrons accelerated by a potential difference of 1 million volts. Afterwards, they were brought back to normal atmospheric pressure, placed in a container, and simply left to their own devices. When examined later, they were seen to be walking about as if nothing special had happened.

If you really want to see something special with respect to Tardigrade survival, try this paper:

Tardigrades Survive Exposure To Space In Low Earth Orbit by K. Ingemar Jönsson, Elke Rabbow, Ralph O. Schill, Mats Harms-Ringdahl and Petra Rettberg, Current Biology, 18(17): R729-R731 (9th September 2008) [Full paper readable online here]

Vacuum (imposing extreme dehydration) and solar/galactic cosmic radiation prevent survival of most organisms in space [1]. Only anhydrobiotic organisms, which have evolved adaptations to survive more or less complete desiccation, have a potential to survive space vacuum, and few organisms can stand the unfiltered solar radiation in space. Tardigrades, commonly known as water-bears, are among the most desiccation and radiation tolerant animals and have been shown to survive extreme levels of ionizing radiation [2–4]. Here, we show that tardigrades are also able to survive space vacuum without loss in survival, and that some specimens even recovered after combined exposure to space vacuum and solar radiation. These results add the first animal to the exclusive and short list of organisms that have survived such exposure.

The experiment was conducted within the Biopan-6 experimental platform provided by the European Space Agency (ESA) during the FOTON-M3 mission in September 2007. During ten days at low Earth orbit (258–281 km above sea level) samples of desiccated adult eutardigrades of the species Richtersius coronifer and Milnesium tardigradum were exposed to space vacuum and two different UV-radiation spectral ranges: UV-A and UV-B (UVA,B, 280–400 nm), and the full UV range from vacuum-UV to UV-A (UVALL, 116.5–400 nm). The experiment included three sets of flight samples: samples exposed to space vacuum (SV) only, samples exposed to space vacuum and UVA,B, and samples exposed to space vacuum and UVALL. All samples were also exposed to ionizing solar and galactic cosmic radiation. Desiccated control samples were kept under ambient laboratory conditions, but otherwise treated in the same way as flight samples. After the flight, the samples were rehydrated and survival and reproductive patterns were recorded. Our experiment included exposure of both animals and eggs of the two tardigrade species (Supplemental data).

Both species of tardigrades survived exposure to space vacuum alone very well, with no significant difference in survival pattern compared to controls (Figure 1A,B). In contrast, samples exposed to the combined effect of vacuum and solar radiation had significantly reduced survival. In samples exposed to the most life-threatening conditions (UVALL), only three specimens of M. tardigradum survived. Among samples exposed to UVA,B, a high proportion (68%) of the M. tardigradum specimens revived within 30 minutes, but subsequent mortality was high. In R. coronifer, only one specimen exposed to UVA,B revived. Thus, exposure to solar radiation had a very strong negative effect on survival.

We found no significant effect of space vacuum on egg-laying in either R. coronifer (Mann-Whitney test, U = 11; p = 0.38) or M. tardigradum (U = 14; p = 0.081). However, surviving UVA,B exposed animals of the latter species had a lower rate of egg laying (U = 16; p = 0.017).

Eggs laid by animals exposed to space vacuum hatched as well as eggs from control animals in R. coronifer (Figure 1C). The same was observed in M. tardigradum, in which also the UVA,B eggs hatched as well as controls. Also tardigrade eggs exposed directly to space conditions showed no difference in hatching rate between vacuum-exposed eggs and controls, with a similar pattern in R. coronifer and M. tardigradum (Figure 1D). No juveniles appeared from eggs exposed to solar light.

This sort of result is one reason why spacecraft intended to land on the surface of another planet, such as Mars, are assembled in a clean room, and subject to all manner of interesting procedures to ensure that no Earth-bound organisms are accidentally transferred to another Solar System body, because some Earth-origin organisms possess a level of resilience that would make them potential contaminants of another planet.

As it is, Bacillus subtilis has exhibited the ability to survive in space for extended periods of time, and is capable of forming resistant cysts allowing the bacteria to re-emerge when conditions are more favourable, which means that scientists have to expend a fair amount of effort extinguishing such organisms if they turn up on proposed spacecraft hardware. Indeed, it's suspected that a few specimens of Bacillus subtilis managed to escape the attentions of the people scouring the Apollo Moon mission hardware, and that some colonies of this bacterium are present on the Moon. Whether they have survived there is open to question, but if they have, then Bacillus subtilis will have exhibited a truly remarkable ability to colonise new habitats, because they will have been living under conditions of high vacuum and large solar UV radiation flux for over 40 years.

[Calilasseia]

We also have [url=http://air.unimi.it/handle/2434/143778]this paper (sadly behind a paywall with eye-watering fees attached):

Tardigrade Resistance To Space Effects: First Results Of Experiments On The LIFE-TARSE Mission On FOTON-M3 (September 2007) by Lorena Rebecchi, Tiziana Altiero, Roberto Guidetti, Michele Cesari, Roberto Bertolani, Manuela Negroni and Angela M. Rizzo, Astrobiology, 9(6): 581-591 (July/August 2009)

Abstract: The Tardigrade Resistance to Space Effects (TARSE) project, part of the mission LIFE on FOTON-M3, analyzed the effects of the space environment on desiccated and active tardigrades. Four experiments were conducted in which the eutardigrade Macrobiotus richtersi was used as a model species. Desiccated (in leaf litter or on paper) and hydrated tardigrades (fed or starved) were flown on FOTON-M3 for 12 days in September 2007, which, for the first time, allowed for a comparison of the effects of the space environment on desiccated and on active animals. In this paper, we report the experimental design of the TARSE project and data on tardigrade survival. In addition, data on survival, genomic DNA integrity, Hsp70 and Hsp90 expressions, antioxidant enzyme contents and activities, and life history traits were compared between hydrated starved tardigrades flown in space and those maintained on Earth as a control. Microgravity and radiation had no effect on survival or DNA integrity of active tardigrades. Hsp expressions between the animals in space and the control animals on Earth were similar. Spaceflight induced an increase of glutathione content and its related enzymatic activities. Catalase and superoxide dismutase decreased with spaceflight, and thiobarbituric acid reactive substances did not change. During the flight mission, tardigrades molted, and females laid eggs. Several eggs hatched, and the newborns exhibited normal morphology and behavior.

Looks like we need to be rather careful to avoid contaminating places such as Titan with Earth based life forms.

[Calilasseia]

And there's more:

Extreme Stress Tolerance In Tardigrades: Surviving Space Conditions In Low Earth Orbit by Dennis Persson, Kenneth A. Halberg, Aslak Jørgensen, Claudia Ricci, Nadja Møbjerg and Reinhardt M. Kristensen, Journal of Zoological Systematics & Evolutionary Research, 49 (Supplement S1): 90-97 (May 2011) [full paper available from here]

Abstract

Most terrestrial tardigrade species possess the ability to enter a reversible ametabolic state termed anhydrobiosis in response to desiccation. In the anhydrobiotic state, tardigrades display an incredible capacity to tolerate extreme environmental stress, not necessarily encountered in their natural habitat. In this study, we determine the effect of different extreme stresses on initial survival, long-term survival and fecundity of selected species of limno-terrestrial tardigrades. The primary focus was to assess the effect of cosmic radiation. This was achieved through the RoTaRad (Rotifers, Tardigrades and Radiation) project on the BIOPAN 6 mission, funded by Agenzia Spaziale Italiana under the European Space Agency. To test their tolerance of space environment, tardigrades were sent into low earth orbit, and exposed to cosmic radiation and a microgravity environment. Experiments on Whatman-3 filters show an effect of cosmic radiation on the survival of the eutardigrade Richtersius coronifer just after returning to Earth; however, after 2 years of desiccation on Whatman-3 filters, none of the tardigrades previously exposed to cosmic radiation could be revived. In a microcosmos experiment, the tardigrades R. coronifer, Ramazzottius oberhauseri and Echiniscus testudo were desiccated on a moss substrate together with rotifers and nematodes. Very low survival rates were observed in this experiment, likely due to the applied desiccation protocol. Embryos of the tardigrade Milnesium tardigradum were also exposed to cosmic radiation; they all hatched in the laboratory after the flight. In addition, experiments testing extreme cold and vacuum tolerance in R. coronifer show that tardigrades in anhydrobiosis are unaffected by these conditions.

[mistermack]

Seems like it's going to be heavily odds-on that some sort of life WILL be there on Mars, if lumps of Earth have hit it in the past. And possibly Mercury too, going by the reports of water ice in the shady craters.

[Jason]

And Venus! and Titan! and Europa!

Fucking supposition! Bah!

[mistermack]

And Venus! and Titan! and Europa!

Fucking supposition! Bah!

I don't know about Venus.
Too hot, even for nematodes and tardigrades, I would think.
Too hot for any kind of water. If Mercury has ice, then it might have liquid water in places.
No chance of that on Venus. Although the upper atmosphere of Venus is actually quite balmy at certain altitudes.

[Calilasseia]

At some point in the past, I think Carl Sagan suggested a possible means of terraforming Venus. Seed the upper atmosphere with highly resistant single celled algae and cyanobacteria, and let photosynthesis deal with the carbon dioxide. Once the atmosphere is breathable, and the temperatures have plummeted from molten lead levels to something more tolerable, start seeding the planet with some multicellular life forms, and start generating some soil. Whether this would work, of course, is another matter. The organisms would have to be capable of performing their normal metabolic functions around 60 Km above the surface, to keep them above the sulphuric acid cloud layer. If organisms could be found that would maintain a permanent colony at that altitude, then terraforming Venus would be possible, but you'd have to wait several centuries for the planet to undergo significant change. Though why anyone would terraform a planet closer to the Sun, as opposed to further away, knowing that at some point the Sun is going to run low on hydrogen and start moving into the red giant phase, is a bit of a mystery.

Terraforming Mars has its own issues. Such as maintaining a relatively thick and breathable atmosphere on a low-gravity world, one with virtually no magnetic field to stop the solar wind from stripping it away. Plus, there's the ethical issues that arise if we find indigenous organisms on there.

[mistermack]

I did read somewhere, a while back, that the upper atmosphere of Venus was the closest known condition to Earth in the Solar System. Temperature and pressure being very Earth-like at a certain altitude.

But if there was a water cycle, I think it would have been detected and mentioned by now.
I would have thought that the turbulence might be high in the hot atmosphere, but maybe not. Again, without water, it might be fairly calm. I expect they have data for that.

Maybe they could design floating helium-filled lightweight structures that could float around the upper atmosphere, and actually colonise it that way. In a dense atmosphere, it might be feasible.

Might be a lot of lightning about though.