Signs of Liquid Water Found on Surface of Mars, Study Says
nytimes.com
nytimes.com
Edit: Here is an article from brown that also draws parallels between Don Juan and Mars: https://news.brown.edu/articles/2013/02/antarctica
NB I learned about the nearby Airdevronsix Icefalls from Antartica - they are really quite impressive:
http://www.wondermondo.com/Countries/An/Antarctica/Antarctic...
"According to the USGS topographical map published in 1977, the area was approximately 0.25 km2 (62 acres). However, in recent years the pond has shrunk considerably. The maximum depth in 1993–1994 was described as "a foot deep" (30 cm). In January 1997, it was approximately 10 centimetres (3.9 in) deep; in December 1998 the pond was almost dry everywhere except for an area of a few tens of square meters."
http://www.worldalldetails.com/article_image/natural_phenome...
Given the latest NASA news about water on Mars, as in, “flowing water on today’s Mars,” I am still trying to figure out how that would work.
If water boils at 79ºF when the atmospheric pressure is lowered to 0.5psi, what would it boil at given Mars’ atmospheric pressure of 0.087psi?
How could Mars, which barely has an atmosphere, support liquid water? Why would not the water basically evaporate quickly if not boil off almost instantly?
The water on mars is probably "salty" mixture, maybe slush, but we don't really know what it's consisted of unless we have measurements / spectral analysis of the water mixture.
We're not going to sterilize our research equipment going to Mars and we're not going to search likely sites where we could find life because we don't want to contaminate them. And yet, looking for signs of life native to Mars (or even water which might support life) is the top reason we're there, judging by the headlines. Seems like someone in NASA needs to work out this conflict.
According to the reddit AMA, NASA does do some amount of sterilization before going to Mars, it is enough to justify the exploratory mission. More sterilization would probably take more man hours, more $$$, which would delay the mission to account for an (estimated) low probability of finding water. It seems like they've chosen to iterate instead of getting it perfect the first time, something we're all familiar with.
"The rovers have been sterilized for their particular landing sites where there's been no evidence of present day liquid water. To go to the RSL rovers will be required to be sterilized to a higher level. We also take samples of microbes that might be on the spacecraft before they're launched, so we can compare with any future discoveries. -RZ" [1]
Apart from that, "These features are on steep slopes, so our present rovers would not be able to climb up to them.-RZ" [2]
They will be working on moving further. Let's congratulate them for this wonderful major accomplishment at least.
[1] https://www.reddit.com/r/IAmA/comments/3mq1wl/were_nasa_mars...
[2] https://www.reddit.com/r/IAmA/comments/3mq1wl/were_nasa_mars...
So true. It's surprising that some commenters, above and nearby, don't stop to think that a decades-long, multibillion-dollar exploration program, with dedicated conferences (e.g., http://www.hou.usra.edu/meetings/lpsc2015/), journals (e.g., http://agupubs.onlinelibrary.wiley.com/agu/jgr/journal/10.10... or http://www.journals.elsevier.com/icarus/) and scientific communities in the many hundreds of scientists, professors, postdocs, and PhD's, has not gone deeper than sophomoric gotchas like in the comment above.
I admit, there is a question here about exploration strategy. The question is how to approach it -- and a little humility and willingness to poke around for information would be in order.
Edited to add: The root for documents pertaining to Mars exploration strategy is here (http://mepag.nasa.gov/reports.cfm) and an excellent reference for contamination control for the upcoming Mars-2020 rover is here (http://mepag.nasa.gov/reports/OCP_2014_final_report_docx.pdf).
Finally, don't miss this deep analysis of the "Special Regions" on Mars (http://mepag.nasa.gov/reports/Rummel_et_al_Astrobiology_14-S...). From the abstract:
"Significant changes in our knowledge of the capabilities of terrestrial organisms and the existence of possibly habitable martian environments have led to a new appreciation of where Mars Special Regions may be identified and protected. The SR-SAG also considered the impact of Special Regions on potential future human missions to Mars, both as locations of potential resources and as places that should not be inadvertently contaminated by human activity."
The irony is strong with this one.
The iteration explanation makes some sense, although these seem like very expensive iterations.
Why not this?
"So, I don't understand what's going on here, this seems weird because of X, Y, or Z, can someone explain what's going on?"
Or this?
"Is NASA really so dumb that they would do X, Y, and Z given that A, B, and C seem to be at odds with that?"
Instead we get: "Hah. NASA is so dumb." Even though we live in 2015 and the results of even 15 minutes of effort involving google and wikipedia could clear up a lot of these misconceptions.
Why are people so heavily invested in maintaining their own ignorance? Why do people insist on jumping to the conclusion that thousands of top tier scientists couldn't POSSIBLY have thought of the same things that occurred to them in the few moments spent thinking about it before deciding to make a post?
You're correct of course that commenters are too quick to make gotcha criticisms when they ought to pause and realize that there's almost certainly more going on. But this is something most people do, and we should each take care of our own part of it first.
There's another aspect of this too. On HN, the problem is as much created by the upvoters as by the commenter. Sometimes a comment was intended as an offhand observation—the sort of thing you'd throw out to friends, not meant to sound authoritative, let alone pompous. But by the time it gets upvoted to the top comment, it can sound like the criticism of an asshole. HN unfortunately has a number of areas like this, where every individual contribution is positive, or at least well-intended, yet the total they add up to is negative. Let's not make the mistake of blaming individuals for a collective problem that we all contribute to.
Why are people so heavily invested in maintaining their own ignorance?
More attacks. Why? Look, I took a 10 minute break to read some HN this morning and read the article. I didn't know all the details and I had to get back to work, so just threw out a speculation. Judging from the 35+ upvotes I received, it was something many others reading the article were curious about.
Why do people insist on jumping to the conclusion that thousands of top tier scientists couldn't POSSIBLY have thought of the same things that occurred to them in the few moments spent thinking about it before deciding to make a post?
I guess you could wonder why you jumped to the conclusion of my thought process because you were wrong. NASA isn't just scientists. Often decisions are made for political, bureaucratic, and budgetary reasons that have nothing to do with the science. Sometimes, smart people do lame bone-headed things.
The concern is that given what we've learned about microorganisms in space, this may not be enough; "Extensively sterilized" is never "Perfectly sterilized", at least, not without building it out of solid metal and annealing it in space. There was also a last-minute variance granted to the drill bit on Curiosity, which was contaminated between sterilization and launch by briefly opening the box in a lower-spec clean room.
http://www.space.com/13783-nasa-msl-curiosity-mars-rover-pla...
As we enter an era of inexpensive launch capacity, the sterilization step is actually so expensive it may exceed the cost of the launch vehicle. There is a case to be made for dropping these protections: They're a barrier in the way of a widespread robotic exploration mission, and a manned mission is going to be implicitly contaminative, since you can't run humans through an autoclave. The most conservative route to detecting life before sending humans is years and years of robotic launches to a variety of regions, with several sample returns. It's arguable, but I'm not sure we have the stomach to do that before the 2030's, there's no sign of the major expansion of NASA funding that would be required for the decade of exponentially escalating robotic precursors to a human mission, on the horizon. Given that we're apparently not going to protect Mars from life, that brings into question why we should bother pretending that's what we're doing today. There have already been substantial transfers on previous landers and impactors.
So I figure that if contamination of Mars by Earth life was a problem it would have happened by the Paleozoic.
I dunno. I agree that something like the K/T impactor probably blasted bits of our planet all over the Solar System, but I suspect the depth of the gravity well brings more factors into play than just "how long it would take for ejecta to get to X". For example, accelerating a bit of surface to escape velocity would involve a lot more energy on Earth than on Mars, and at the point of impact I'd have thought that energy would translate to possibly-sterilizing heat.
As to larger impacts I really can't speak with any authority and I'm not aware of any studies which would say. But my intuition would be that the greater volumes in large the ejecta from large impacts would heat up less due to more insulation. I should probably put this on /r/askScience and see if anybody knows more.
Furthermore, what if life on Mars were fragile enough that Earthly microscopic organisms destroyed it?
Besides, if there are primitive life forms on Mars, it's quite presumptuous of us to assume we could so easily wipe them out.
Mars becomes infinitely more interesting if it can become a host for terrestrial life.
It's not like we should care about the consciousness of microbes. What he meant, as I read it, is that if there are microbes we'll want to sample them and study them BEFORE we change the landscape and possible kill them.
I don't think we want to contaminate or destroy our only source of knowledge on other kind of life.
May be we can do that later, once we study them enough or have kept it enough for further study. But let's not make our first decision be "We gonna destroy it someday anyway, let's just stomp on it carelessly right now"
Finding a life outside of Earth will be one of the greatest discoveries of man kind, something that will never be overshadowed by anything. They want to make sure that when we'll find something it didn't catch a ride on what ever we sent to find it.
Eventually when we start exploring space it wouldn't really matter, yes some precautions might still be kept but we wouldn't take as much care as we do now.
I for one also do not see humans contaminating an alien ecosystem as something unnatural, humans evolved, they've spread out, they seed life (intentionally or otherwise) this is just as much of a natural process as the potential for comets and meteorites to seed solar systems and beyond with organic compounds and even life it self.
There would definitely be a difference vis-a-vis reconstructing the natural history of Mars.
Suppose some biological particle makes it to mars. Then we pick it up, discover that its very dead already, DNA sequence it and find that it matches the common flu. Write it off as contamination, rinse & repeat until we find something that is alive & looks like green men.
Or can science genuinely not distinguish earth contaminants vs alien life?
That seems almost comically improbable, but given that we've found that lichen can survive in the vacuum of space for a year and a half [1] and the mere existence of life on hydrothermal vents and inside Chernobyl[2], I think we can safely say that life is surprising.
[1] http://www.astrobio.net/topic/origins/extreme-life/lichen-or... [2] http://web.archive.org/web/20080424001002/http://www.science...
The only loss I can see is the lost opportunity to study a truly alien ecosystem in detail, but if we can't study it without fatally contaminating it, that was never really a benefit we could enjoy anyway.
I'll make my thinking more explicit ...
The best case is that we either a) don't introduce microbial life, or b) it just flat-out dies. Then we can examine Mars for signs of life (current or historical).
The worst case is that we contaminate Mars with microbes that flourish there, forever destroying our ability to examine Mars for signs of life.
I'm assuming we can't explore Mars without risking the worst case. So it seems worthwhile to try; the very worst case is that we replace a Martian microbial ecosystem with one from Earth.
Another way to look at it is that Mars seems to have almost no biodiversity, so it's possible that martian life forms may be well adapted to their environment, but not for competition. Terrestrial microbes have evolved in an utterly brutal competitive environment and they've been shown to adapt to extreme conditions, so it's not unthinkable that they may have a substantial edge over martian life.
Maybe. Just a laymen, so I could be totally wrong.
Something could survive the trip, grow, be found and still be entirely unknown to us. And it probably wouldn't be all that unlikely.
Take this study, that swabbed people's belly buttons and found thousands of unknown bacteria, bacteria only found before in foreign countries the person had never visited and "extremophile bacteria that typically thrive in ice caps and thermal vents"
http://www.theatlantic.com/health/archive/2012/12/1-458-bact...
All equipment leaving Earth is sterilized. The thoroughness of sterilization varies from project to project, instrument to instrument, and the agreed to HW & Planetary Protection Plans. It helps ensure that equipment is not giving false readings. Serious money is also laid out for HW & Planetary Protection (there's a whole division of probably 150 people at JPL) and sophisticated equipment used to test for contamination.
However, if there was deviation from the original Planetary Protection Plan [1], it was likely to execute some other test, timing/scheduling conflict, or some other "administrative" reason.
And with respect to finding water on Mars, why would you send your robot to a polar cap or even a "lake" with visible/detectable water? If you're attempting to prove that water and water flow processes exist & are active on Mars, it's probably better to test a fringe area, hence, the 3.3m requirement.
[0] https://news.ycombinator.com/item?id=6809134
[1] http://www.space.com/13783-nasa-msl-curiosity-mars-rover-pla...
Should that read all equipment leaving Earth from the United States? Do other countries with developing space programs adhere to the same practices? Does the US have agreements with other countries to make sure we're all on the same page so to speak?
But to answer your first question, Yes. All HW & Planetary Protection practices are not equally applied by all collaborators. However, ISO 14644-1 [3] is now a 15 year-old standard, at least, for Clean Room work environments. Such practices and the HW & Planetary Protection Plans are for Project Managers & Principal Investigators to manage & implement. "Faster, Cheaper, Better; pick any two" [4] we always said in the Spacecraft Assembly Facility at JPL.
Agreements are in place for all projects, and, it usually in the Principal Investigator's best interest to ensure his instrument/subsystem has the best HW & Planetary Protection Plan in place. It ensures their instrument/subsystem is operating nominally and has the longest usable life possible.
[1] https://en.wikipedia.org/wiki/Cassini%E2%80%93Huygens#Huygen...
[2] https://en.wikipedia.org/wiki/Mars_Exploration_Rover#Related
“These are ongoing conversations,” said Catharine A. Conley, NASA’s planetary protection officer, who coordinates the efforts to minimize the chances of life inadvertently crossing the solar system.
Sorry, still not making sense.
"Office of planetary probe sterilization" would be much more descriptive. Otherwise we're taking on a helluva lot more authority and prerogative than we probably should.
Note, the concept of "Planetary Protection" also applies to contamination in the reverse direction for sample-return missions, which are very much expected to be part of Mars 2020.
I didn't know this before looking, but it turns out there are UN agreements, and something called the "Outer Space Treaty" to which the U.S. is a signatory (1967). This treaty, in essence, prohibits "harmful contamination" of other planets. There is a body of scientists (a panel within COSPAR) which deliberates on contamination and issues guidelines in a timely way. ESA also has a policy. So there do seem to be players here that are larger than Elon Musk.
But these agreements are subject to revision and negotiation as more becomes known. Presumably something will be worked out as the reality comes nearer.
One would hope so. I must point out that private space travel was entirely out of the question with NASA for many years. It's only been very recently that the idea has started to catch on -- and it's not universally lauded across the agency. Gotta wonder what kind of obstacles we're currently setting up (perhaps without fully realizing it) for anything beyond LEO.
[Sec. 6]
"Strong interest exists among various countries and private industries to send humans to Mars, both for short-term exploration and long-term colonization." (and on for 3 dense pages).
So, private ventures are part of their deliberations.
[Sec. 8, end]
"It will be impossible for all human-associated processes and operations to be conducted within entirely closed systems, so protocols need to be established so (1) human missions to Mars will not contaminate Special Regions nor be contaminated by materials (or possibly organisms) from them and (2) human activities on Mars will avoid converting Non-Special Regions to Special Regions and thus help control the spread of terrestrial microorganisms on Mars."
*
The basic strategy is to identify and avoid "Special Regions".
Since all current private industry space efforts are still organized with NASA, I imagine this part of NASA is involved with efforts such as SpaceX as well.
Perhaps it's not so much of a conflict as a multi-staged approach...
The non-sterile equipment is currently roaming around and has just said "Hey! There's probably water and maybe life over there!" and now we get to build something to go poke at it with a sterilized stick.
Another take @ http://www.marssociety.org/home/about/faq/
Q: What are the risks of contaminating Mars with Earth life forms, or vice versa?
A: Actually, it is arguable that this has already been happening for billions of years. During his study of known Martian meteorite ALH84001, Cal Tech's Joseph Kirschvink showed that large parts of the rock were never heated above 40C (104F), proving the theory of University of Arizona researcher Jay Melosh that it is possible for rocks to be ejected from one planet's surface and land on another's surface without being excessively heated. More importantly, this discovery showed that not all rocks ejected from either Mars or Earth are sterilized -- a fact that, when combined with the known ability of microorganisms to remain alive in a dormant state for millions of years, means that Earth life has probably already traveled to Mars, and if life ever existed on Mars, it has already traveled to Earth.
Additionally, only recently have we been able to construct rovers that could host the equipment necessary to reliably detect and study Martian life, so the level of sterilization that we've been using hasn't been a problem.
It doesn't matter anyway, as some microorganisms are known to endure exposure to open space for years. Sterilizing Curiosity would likely be impractical (its size and weight are comparable to a small car, which is much larger than a potato). A smaller probe designed for finding life and only that could be a safer bet.
Besides, we're on another planet. If our payload was nothing but the nastiest chemical we could come up with, we still couldn't ship enough to Mars for it to matter.
No, the only payload that could conceivably be harmful is one that can self-replicate, which at this juncture means life. (Ask again in a hundred years.)
---
For sterilization, they will probably use gamma rays. They are strong enough to break a lot of chemical molecules, and then kill all the bacteria. But the gamma rays are not strong enough to break the atoms nuclei or make them radioactive. So the rover will be sterilized but not radioactive.
This is similar to the process that irradiate food with gamma rays. You can store them in a perfectly sealed place without refrigeration and they a are safe to eat because they don't have bacteria and they don't have radiation. So this is a safe method. More info: https://en.wikipedia.org/wiki/Food_irradiation
---
Another different radiation process is to irradiate it with neutrons. It kills the bacteria but it also may make some nuclei radioactive. (I don't know the necessary doses, so perhaps this may be safe, but I'd be much more careful. Something like this is used to treat cancer. Also, this don't produce a lot of radioactive atoms, and the rover is small, so the radioactive material will be not too much. Anyway, as I said before, I'd be much more careful.)
---
Another possibility is mixing the food (for example a tea) with some radioactive material (for example plutonium). This kill the bacteria but also may kill whoever takes it. If you are very careful with the doses, you may use something like this for medicine applications (for example with radioactive iodine). But I guess that if the dose is low enough not to kill the patient, it will not kill all the bacteria. This is definitively not the method they may use to sterilize a rover.
maybe it is just media that needs to work out this conflict.
And it won't be the former case, for obvious reason.
But "we don't have enough data yet" still seems like a good answer to the Fermi Paradox anyway.
This dose of realism dampens my enthusiasm slightly, but if we can find such clear signs of water via satellite image I think it is a great indication that water is more present at the surface than previously thought.
>“If it was too salty, they would be flowing year round,” Dr. Stillman said. “We might be in that Goldilocks zone.”
Mars became geologically stable before Earth, so it could have been the earliest place for life. Then Martian meteors infected Earth.
The best situation I can think of is a catastrophic volcanic explosion which launches a chunk of the planet into space, but that still sounds far-fetched to me.
That planet is Earth. The real Earth. We perceive our ecosystem as friendly only because we've co-evolved with it. It is in objective terms a vicious, vicious place, with every cubic centimeter of any useful resource contended for by thousands or millions of organisms, fighting each other in every conceivable chemical, biological, and physical manner, and in particularly sophisticated corners of the Earth ecosystem, even social manners. It may look peaceful from the apex, but it's not when you get close.
The likelihood of some sort of Martian bacteria getting here and causing amazing problems can never quite be eliminated, but it's very, very low. Plus, if Martian life ever existed, it actually won't be entirely disconnected from Earth life due to what you could call "transpermia": http://users.tpg.com.au/users/horsts/swaprock.html
In fact if life is discovered on Mars, the next question is whether it is just Earth life that hitched a ride and managed to adapt to conditions that aren't necessarily all that much harsher than conditions we've found life on here on Earth. It's interesting either way, but the implications are hugely different between some hitchhiking Earth life vs. life that clearly came from a different abiogenesis event.
Of course martian life could be different than terran life, and that would be interesting too. But there are reasons to suspect that liquid chemical reactions was necessary at the genesis of life, and water is a uniquely optimal liquid for this purpose.
A martian virus is unlikely to do anything to your immune system. For one thing it is unlikely that the virus would even use the same genetic codes (A C T G) as terran DNA, unless we share a common ancestor, and even in that case it wouldn't do anything against you & your immune system would eventually create an antibody and wipe it out. We fear things like bird flu and swine flu because they develop in close proximity to humans in analogous systems, honing attack vectors specifically targeting some weakness of the animal body. An alien virus would likewise be good at attacking aliens, not us.
"Life" is a bunch of chemical processes. A necessary prerequisite is therefore a solvent in which those chemical processes can occur, and which can move substances around, whether it's within a cell, an organism, or an environment.
Of all the potential solvents, solids can't move stuff around, and in gases, only volatile and highly concentrated substances would have a chance to react. It's also too easy to move around in a gas: potential gas-based "life" would just...fall apart.
So the solvent and carrier being a liquid is also likely a prerequisite for life. It also has to stay a liquid at a relatively wide range of temperatures, and be abundant enough so that all the rare coincidences that might lead to life have a chance of happening and perpetuating.
Water is the only molecule that fits the bill, and happens to be the second most common molecule in the universe.
For one why, look up amphoteric and zwitterion. Water has a super convenient pH range where about a ten millionth of pure water self ionizes aka ten to neg seventh or pH of 7, and all kinds of super convenient reactions occur above and below that pH and its really easy to manipulate ionization rates around that level without using too much. You don't need just a liquid but one where you can really screw around with something like amino acids by easily and cheaply changing the ionization rate of the liquid. So there are super convenient chemical reactions that depend on the ionization level of the liquid and its really easy to manipulate water. Conveniently water "just works" without having to add tons of other stuff to it.
Liquid methane isn't polar enough to really be useful when messing with ionic substances (table salt, etc). Whatever you use for a liquid, it needs to be polar so ionic stuff like salts can dissolve. It turns out that interesting chemistry doesn't happen with non-polar substances at normal temps; thats why when you bury stuff for a couple million years the only thing left behind undecayed (more or less) is non-polar hydrocarbons (crude oil). Ammonia is polar but has other issues.
The hydrogen bonds are important. Water should be a gas at room temp. Really, it should, looking at bonds and molecular weight and stuff. Yet the hydrogen bonds that form keep it liquid at room temp. So you get "gas speed" chemical reactions at "high" room temperature, yet its liquid to a ridiculously high temp.
Maybe some custom liquid silicone with some bolted on weirdness could make a useful artificial blood plasma or "stuff" for life to live in. How it would make it without the chemical plant being made first is mysterious.
A lot of the common molecules aren't good solvents or react too readily with other common elements or molecules, like oxygen or halogens. And molecules that are good solvents just aren't common enough to dissolve much of anything.
Methane would probably only work in an oxygen-deficient environment, and ethane wouldn't form enough by coincidence to be a meaningful solvent in comparison to methane or other simple organics.
And it just so happens that H2O is very common and a great solvent, so any other potential solvent would probably have a little water in it anyway. And if it's there, a lifelike chemistry complex would probably make use of it in some way.
As to the first part, there are uncountable examples of water-based life, and zero examples of non-water-based life. That doesn't rule out its existence, but basic chemistry makes it unlikely, and it won't look anything like life as we know it. No other liquid has the properties needed for any kind of life observed.
As to the second: https://www.google.com/search#q=%22second+most+common+molecu...
You're going to have quite a lot of H, some He, and ever decreasing quantities of larger atoms. The abundance of atoms in our galaxy by mass is 74% H, 24% He, 1% O, 0.5% C, 0.1% Ne & Fe & N, 0.05% Si & Mg & S. When you break it down by quantity of atoms, the spread only grows wider. 92% H, 7.5% He, 0.1% O, 0.05% C, 0.01% N & Ne, and ~0.003% Mg & Si & Fe & S.
Now, for each atom, you're going to work the room at the universal party. If you're an H, you show up early to the party, and you're very likely to run into another H and really hit it off. So most of the H in the universe is going to pair up as H2 before anyone else even shows up. He and Ne don't really want to be at the party. They hang out in the corners and stare at their own quarks. So let's just pair up all those H atoms into H2 and ignore the He and Ne.
We're now at 99.6% H2, 0.2% O, 0.1% C, 0.02% N, ~0.005% Mg & Si & Fe & S among atoms that actually want to bond.
So C, N, Mg, Si, and Fe are pretty chill. If they happen to meet up with a lone H, they get along together pretty well. Otherwise, they're content to circulate around the party and meet other atoms looking for a good bond.
But O and S are a little crazy. They are not going home alone, ever. And usually, they're going to hook up with the first other atom (or molecule) they meet at the party. Almost every O that joins the party is going to end up as the meat in an H sandwich and leave the party. By coincidence, some will become O2 and be content. A bit less will become CO, or NO, and a very tiny amount will end up in MgO, SiO, FeO, or SO. And those will stay at the party, looking to bond more.
So just by random meetings based on relative abundance, it is clear that H2O is going to be third among discrete chemical units, and second among bonded molecules. If O were less abundant, or less ravenous for electrons, it might be different, but it's pretty safe to say that O will try to react with anything it meets, and it's very likely to meet an H2.
As far as I understand it's much easier for us to know distribution of different elements that it is to know distribution of different molecules in the universe. I assumed that it wouldn't be that popular given that it does not take part in a nuclear fusion.
The most common molecule is diatomic hydrogen and the second most common is helium. That'll likely be true for hundreds of billions of years, if not trillions, due to the way stars burn their atomic fuel. Even if you don't include atomic helium as a molecule, the second most prevalent would likely be the most reactive combination of hydrogen and nitrogen/carbon.
https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elem...
Also see this delightful comment by logfromblammo: https://news.ycombinator.com/item?id=10292067
Assuming your definition holds: Do you have an actual (peer reviewed) citation that demonstrates that H2O is the second most prominent molecule in the universe, for any real definition of molecule? If not, do you have a citation showing that diatomic oxygen is less likely to form than water in the interstellar medium (considering the momentum of hydrogen atoms will be significantly greater than that of oxygen atoms and thus impact the chemical reactions drastically)? If not, do you have evidence to show that our capabilities to detect polar molecules like water are able to account for the absurd abundance of nonpolar molecules (for which electromagnetic detection is practicaly impossible) based solely on first principles of astro or even quantum chemistry?
I'm not trying to play devil's advocate or prove you wrong. These are questions I'd love to have the definitive answers to but I'd rather have no answers at all than a random HN post which only cites a Wikipedia article on the prevalence of atoms (not molecules, missing the entire point of chemistry) and another unreviewed HN post on astrochemistry from first principles without a single significant citation.
The purpose of [citation needed] is not to take the wind out of your statement but to force you to provide the necessary evidence to back up your assertion.
No it doesn't; https://en.wikipedia.org/wiki/Molecule cites that as an earlier, less precise definition than the one that's commonly used today. The definition right at the top of the page is quite clear that by the usual definition, a single atom by itself does not constitute a molecule.
> The purpose of [citation needed] is not to take the wind out of your statement but to force you to provide the necessary evidence to back up your assertion.
In polite discussions, attempting to "force" your conversational partner to do anything is kind of discourteous. If you're honestly seeking information, then by all means feel free to ask questions. But whether you intended to or not, your responses are coming across as very adversarial and dismissive.
> In the kinetic theory of gases, the term molecule is often used for any gaseous particle regardless of its composition. According to this definition, noble gas atoms are considered molecules despite being composed of a single non-bonded atom.
Unless you're saying that water (or any other molecule for that matter) can form inside of a star, which would open an entirely new field of chemistry, this is the definition to use when talking about astrophysics.
Diatomic oxygen is extremely rare in the universe, because it's extremely unstable. Oxygen would rather be bonded to pretty much anything rather than itself, including hydrogen. [citation: go burn some hydrogen]. It's common round these parts due to some rather bizarre nonequilibrium chemistry [aka life].
What we know about the prevalence of various molecules is a combination of what we know about the prevalence of atoms combined with what is thermodynamically stable. It goes hydrogen, water, methane, ammonia, carbon monoxide, I think? At this point it depends on local conditions, temperature and so forth, but the stability of water combined with the prevalence of oxygen makes it basically unassailable as the second most common molecule after H2.
Can you see why instead of "forcing someone to provide references" it would be better to ask someone nicely for references?
If you can't provide a single citation to support such fundamental statements as "H20 is the second most common molecule in the universe" outside of irrelevant Wikipedia articles, they are worthless, HN moderator and community standards notwithstanding.
[0] - https://en.wikipedia.org/wiki/Carbon_monoxide
[1] - https://en.wikipedia.org/wiki/Nuclear_fusion#Nuclear_fusion_...
True, we've only seen water-based life firsthand, but our "sample" of reality is so infinitesimally minute relative to the whole that we cannot properly use that as a basis to make assertions about what the overall proportional makeup of types of life might be. Doing so is pure speculation.
It would be sort of like randomly picking up one tiny pebble at random from anywhere on the earth, identifying its elements, and then concluding that it's "unlikely" any other non-identified elements exist on the entire planet because they aren't in that particular pebble.
So while we shouldn't exclude the possibility, "life as we know it" is the most sensible place to start.
So let's just spread life intentionally. It seems like that is one of our goals anyway -- not necessarily for governments (ie. NASA), but certainly for private space flight.
That doesn't preclude eventually spreading life to Mars. Even if living indigenous bacteria, or even plant life(!) were found - I think this is the most ambitious scenario now conceivable, the 'Mars mat' of fiction suviving in caves - it likely wouldn't be an argument to stop colonisation, though it might have bearing on arguments about terraforming.
On the other side we should consider the possibility that space is porous to life. That life is able to travel between bodies or on bodies that pass through the vacuum of space. In this case we should expect that while there may be independent origins of life, within relatively short distances a certain kind of biochemistry might come to dominate.
Add to this the quite important role that exogenous organic chemicals likely played in the emergence of life on earth, in the case where life arose here and on mars independently. It is probably more likely that life would emerge through roughly the same processes wherever it emerges, therefore in roughly similar environments and using roughly the same building blocks (organic molecules constructed in space and deposited through impacts) we might expect it to have similar forms. I would say that Titan is likely to have something entirely different to earth life - owing to it's very different environment...
Additionally, electrochemical gradients as a means of storing and using energy, and amphiphilic bilayer based membranes both seem to be incredibly fundamental, it would be more surprising to see life that was based on other principles than to see life that shared the same design. As for everything else, who knows? It's likely there are a ton of alternative design choices for a lot of different aspects of cellular machinery on up to large scale structures of plants, animals, fungi, etc.
But overall I'd rate some of the more "out there" notions of things like silicon or sulfur based life, or merely carbon-based life that was utterly different from our nucleic acid/protein/membrane based life as being comparatively unlikely.
Imagine it is completely distinct, and doesn't have cells.
> “There are two basic origins for the water: from above or from below,” Dr. McEwen said. The perchlorates could be acting like a sponge, absorbing moisture out of the air... The other possibility is underground aquifers, frozen solid during winter, melting during summer and seeping to the surface.
Although "rain"/humidity is unlikely, the article also discusses why it can still be considered a possibility since we don't have good humidity measurements at the surface.
So the highly publicized 2010 study is now pretty much falsified.
http://www.nature.com/news/arsenic-life-bacterium-prefers-ph...
Mmmmhh... Since when does NASA need a press conference?
The scientific papers that outline this analysis was already available in astronomy circles - the Nasa event is the press conference letting the bigger community know.
It's not like it's a secret! All the measurements were already made by the Orbitor and is presumably analysed by researchers around the world prior to this unveiling.
This is NASA we're talking about, right? ;)
Unfortunately it's also all but inevitable that we'll bring some with us, if we haven't already. Life is persistent, and ever-surprising.
But there are Mars rocks that have been busted loose from Mars, and orbited down to Earth.
https://en.wikipedia.org/wiki/Sabatier_reaction#Manufacturin...
I guess also wrapped into my statement was the thought that to be able to launch something back it would have to be landed very well and require some very complex machinery to prepare for launch, given the success rates of just being able to land something on Mars without it breaking. I went with the first reason off the top of my head :)
It's hard to justify the required R&D expenses without appealing to emotion (such as sending humans).
But I think it's safe to assume it's quite fragile at the very beginning, and therefore conditions must be milder for it to appear at all.
Once it takes off it's probably much more sturdy.
Yep. Here's a great book on the topic:
http://www.amazon.com/Travelers-Guide-Mars-William-Hartmann/...
It may still be that life is so unlikely that it only happens on one out if every billion planets where the right conditions exist.
My favorite best-evidence-yet-of-water-on-Mars was that time the Phoenix robot scooped up an ice cube and took a picture of it.
> NASA Spacecraft Data Suggest Water Flowing on Mars > 08.04.11
2008: NASA Spacecraft Confirms Martian Water, Mission Extended http://www.nasa.gov/home/hqnews/2008/jul/HQ_08_195_Phoenix_w...
2009: Meteorite Impacts Expose Ice on Mars http://science.nasa.gov/science-news/science-at-nasa/2009/24...
2010: NASA Trapped Mars Rover Finds Evidence of Subsurface Water http://www.jpl.nasa.gov/news/news.php?release=2010-355
2011: Observations from NASA's Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest months on Mars. http://science.nasa.gov/science-news/science-at-nasa/2011/04...
2013: Curiosity's SAM Instrument Finds Water and More in Surface Sample http://www.nasa.gov/content/goddard/curiositys-sam-instrumen...
2014: New Evidence for a Mars Water Reservoir http://science.nasa.gov/science-news/science-at-nasa/2014/19...
Fourth link isn't conclusive
These results are the closest scientists have come to finding evidence of liquid water on the planet's surface today.
The last link summarises that liquid water has not been conclusively found yet, and it is the most recent:
While recent orbiter missions have confirmed the presence of subsurface ice, and melting ground-ice is believed to have formed some geomorphologic features on Mars, this study used meteorites of different ages to show that significant ground water-ice may have existed relatively intact over time.
Curiosity’s observations in a lakebed, in an area called Mount Sharp, indicate Mars lost its water in a gradual process over a significant period of time.
So none of your links contradict what the person you are replying to said.