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Rover Exiting Crater To Continue Martian Marathon
Riding with Robots writes "The robotic geologist Opportunity has nearly reached the rim of Victoria Crater, which it is leaving after a year of exploration inside. Rover handlers decided to abandon attempts to approach the crater's cliff walls when they saw a power spike similar to the one that preceded a broken wheel on its twin, Spirit. Opportunity is already making do with a stuck robotic arm. The mission's manager said, 'Both rovers show signs of aging, but they are both still capable of exciting exploration and scientific discovery.' Opportunity is set to continue trekking across the Meridiani Plains of Mars, even though its wheels have already seen 10 times the use they were designed for. Meanwhile, Spirit has survived yet another harsh Martian winter to produce another striking panorama."
Adam Korbitz notes other Mars-related news that funding has been approved for the Search for Extra-Terrestrial Genomes (SETG) Project. The project was one of 15 selected to receive funds through a NASA research opportunity program. The stated goal of the proposal is to "develop a PCR detector for in situ analysis on other planets, most immediately, Mars. This instrument is so sensitive it should allow the detection very low levels of microbial life on Mars, and will determine its phylogenetic position by analysis of the DNA sequence of the genes detected in situ."
PCR requires 2 primers of known sequence, roughly 20 bases long, between 100 and 1000 base pairs apart. Given that we have absolutely no sequence information from which to design these primers, how do they expect to do PCR on completely unknown DNA?
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Using the DNA samples from Area 51 that we obtained from the Martians that crash landed in Roswell, of course. Duh.
so.. we all know what would happen if Microsoft designed a motor car, but what would happen if the Rover Team designed one?
(I don't know about you, but I think still working after 4 years is damn impressive)
Are there any key lessons to be learned from these rovers' success? Or is it simply that they have no critical consumables (being solar powered and all) and they evidently were overengineered? I guess for starters, having redundancy and the ability to turn off failing components is good, seeing as they're six wheel drive and one of the rovers is now dragging a bad wheel around. What else has been learned from these rovers about engineering long-lasting probes?
WTF? I think we should first concentrate on finding something that somewhat resembles our microbial life before we spend a lot of government funds to ship a PCR detector there.
Not only do they assume that life there has genes in about the same way as ours but also that they are made from the same nucleotides. What would be the odds of that? (excluding panspermia and so on).
As long as there are slaughterhouses, there will be battlefields.
"...the Search for Extra-Terrestrial Genomes (SETG) Project..." Sigh. I read that as "the Search for Extra-Terrestrial Gnomes Project". It's late. I'm tired. Perhaps I should stop coding now...
It's much worse than that. What makes them (or you) think that alien life will have any DNA at all?
They seem to be assuming that alien life will share a common ancestor with Terran life. This seems like a pretty dubious assumption to me.
The most rabid believers in American Exceptionalism are the exact same people whose policies are destroying it.
16S RNA gene PCR, the most sensitive detector for life on Earth
This detector is an amplification strategy called the Polymerase Chain Reaction (PCR) that is based on artificial replication of DNA. PCR is a technique which is used to amplify the number of copies of a specific region of DNA, in order to produce enough DNA to be further analyzed. In order to use PCR, one must know the exact DNA sequences which lie on either side of a given region of interest in DNA. One need not know the DNA sequence in-between. A DNA sequence is the precise order of appearance of 4 different deoxyribonucleotides. The 4 components are: Adenine, Thymidine, Cytosine and Guanine, abbreviated A, T, C and G, respectively. The arrangement of this 4-letter alphabet is the DNA sequence.
The PCR strategy for life detection emerged from the exploration of the diversity of life, which revealed about 500 Ã'universal genesÃ" that are carried in the DNA of every known living thing on Earth (7). The gene that has changed the least over the past 3-4 billion years is the 16S (or the related eukaryotic 18S) ribosomal RNA gene. Ribosomal RNAs are the main structural and catalytic components of the ribosome, a molecular machine that translates RNA into proteins (8,9).
It is the slow rate of change of the 16S gene that makes it the best detector of life. Within the ~1500 nucleotides of the 16S gene, there are multiple 15 to 20 nucleotide segments that are exactly the same in all known organisms (8). These regions of the 16S gene are essential for its catalytic activity and have remained unchanged over billions of years (8).
The technology of PCR involves adding stable 15-20 nucleotide long DNA primers, a stable enzyme nucleotide triphosphate monomers, and a simple heat pump that thermally cycles 20-30 times in 2 hours. To amplify 16S genes from a crude sample, universal DNA primers from the ribosomal RNA gene that are about 18 bases long, oriented towards each other, and about 1000 bases apart are added to crudely purified DNA isolated from an environmental sample (for example, 1 ml of sea water or 1 gram of earth). For the ribosomal genes, the DNA primer 5Ã GTGCCAGCAGCCGCGGTAA 3Ã which corresponds to nucleotides 515 to 533 of a ribosomal gene, and 3Ã TTCAGCATTGTTCCAWYGGCAT 5' which corresponds to the base pairing complement of nucleotides 1492 to 1510 are added to an extract prepared from soil (M, Y, and W are codes for mixtures of two such nucleotides necessary to capture all 16S genes). Upon heating to 95ÂC and then cooling to 55ÂC, these DNA primers pair with their complement on each DNA strand, even if there are only a few DNA molecules in a sample. After heating to 75ÂC, the DNA polymerase will polymerize the nucleotide monomer components also in the tube to duplicate the DNA strands. There will now be four strands, where originally there were only two. If one repeats the thermal cycle with all the same components in the same tube, now there will be eight strands; repeat again - now 16, etc. Thirty cycles will produce one billion (230) copies of the original sequences. Because the DNA polymerase enzyme used derives from a thermophilic microbe, it can survive repeated cycles of heating to 95ÂC. The amplified DNAs from the PCR can be analysed for size or DNA sequence. PCR will even amplify complex mixtures of 16S ribosomal RNA genes from communities of organisms in environmental samples. Thus, PCR with DNA primers corresponding to the conserved elements can be used to amplify DNA from any species more than a billion fold, without need to isolate, culture, or grow the organism in any way (9).
Because they have to start somewhere? It isn't unreasonable to think that most naturally occurring forms of life are based on DNA. Yes, that is an assumption that could be wrong. We have one data point to work from. If our assumption is wrong, we can create different methods of detection other types of life.
My question to you: what kind of machine would you put together that would search for microscopic life forms that are of a type we have yet to imagine? When you answer this, then you can mock the article's approach.
See my journal for slashdot ID's by year. Mine created in 2005. http://slashdot.org/journal/289875/slashdot-ids-by-year
I wish NASA would get off the "looking for ET life" kick. The probability of finding any sort of life on Mars is vanishingly small. I suspect that NASA knows this, but thinks that it can capture the public's imagination (and thus pocketbook) by pushing the whole "Searching For Life" thing. There are so many other experiments we could do that have a much higher payoff.
I don't think the search for life is going to fire the public's imagination more than the cool photographs they get back. If they *really* want to get the public excited, send an HDTV recorder up there to zoom around... maybe even stereo HDTV so we could see 3D. Let me see a Martian sunset. Those are tactile things that everyone can be excited about. The search for life is an endless string of boring failures. Sure, if it *did* succeed, it would be immensely exciting, but that's like saying it would be exciting to win the lottery, instead of paying the rent. Except winning the lottery is a lot more probable.
Sometimes it's best to just let stupid people be stupid.
I think that's a ludicrous assumption. A reasonably safe assumption is that most life in the Universe is carbon-based, simply because carbon is capable of making the largest and most complex molecules. There's no reason I can think of to think that the end result of any abiogenesis process has to be DNA as the replicating molecule. Carbon can probably be used to produce all sorts of replicating molecules.
The world's burning. Moped Jesus spotted on I50. Details at 11.
They would use random primers. A DNA hexamer (six-base sequence) is sufficiently long to serve as a PCR primer, but short enough that it would take only 4096 different types of molecule to comprise all possible sequences. Of course, we don't want the sample DNA to be plastered in our primers, so we'll pare those 4096 down to a handful, at least one of which, in any sample sequence of significant length, will nonetheless find somewhere to anneal. Once we've gone through enough cycles, it's likely that we'll have amplified at least some segment of the sample DNA. Then, getting the reaction contents purified and sequenced is simply a matter of applied microfluidics.
But without all the poverty.
- Zav - Imagine a Beowulf cluster of insensitive clods...
Use random primers, just like you do for reverse transcription when you want to pick up all the RNA sequences in your sample. The reaction's efficiency would take a hit, but if all they want to do is detect DNA (or maybe even sequence a few very short sections) it could probably be made to work.
A bigger problem is the enzyme used in the PCR. IANABiochemist, but I'd expect the PCR to only work if the Martian bugs hava genomes based on double-stranded DNA chemically very similar to ours.
There are plenty of stable nucleotides that could work as components of DNA but, for some reason, aren't used in Earth's life. Ditto chirality: Using the same constituent atoms, one can build almost identical but left- or right-"handed" versions of molecules. For some reason -- probably just chance -- Earth's life is based on "lefthanded" molecules, meaning that we can't produce or consume right-handed molecules. For example, if we synthesise right-handed sugars (easy for a chemist to do, but expensive), they have the same chemical composition, melting point etc, but the structure is such that our enzymes can't use it as a source of energy. Heck, even the sequence of any DNA scooped into the chamber will be important, as if influences the reaction conditions you need for the PCR to work.
If there is life on Mars, this test would only be able to detect it if Martian life is spookily similar to our own. Which would, I'll admit, be even more exciting than just "life on Mars" because it would hint toward evidence of Panspermia or possibly some sort of fundamental rules about what life is able to look like.
A microscope.
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We don't know how life arose on Earth but the assembly of complex self-reproducers from simpler compounds doesn't seem like any everyday occurrence. We do know that material can be transferred from Mars to Earth and possibly vice versa. So if we find life on Mars we have three scenarios:
A simple application of Bayes' theorem tells us that the first is the least likely.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
http://www.marccarson.com/images/slashdot-mars-panorama.jpg
There you go...491KB.
Kind of like the microscope on Phoenix? http://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080814.html
100nm resolution. DNA however is only 3nm wide.
Well.
a) Working point for life is liquid-solid
b) To form structures, valence bonds are suitable
c) Combinatorics requires more than two valence bonds to make different molecules
d) bonds should be strong in comparison to temperature, yet not forever
All this make carbon a pretty likely candidate to be involved. Hydrogen is painly so abundant that it *will* be involved and oxygen is also not seldom. So it is not unlikely that life somewhere else may be based on a cemistry similar to ours.
Yeah, forgot to mention my source image was from a friend who used to be in the Republican Guard...he says NASA always edit their panos before the public see them. Some of their cattle mutilation images from Titan are pretty impressive.
Their working hypothesis (spelled out on the linked page) is that early in the development of microbial life there is (they claim) a statistically relevant chance that microbes developed on either Earth or Mars could have survived transfer from one planet to another via "meteoric exchange", which there would appear to have been a lot more of back ~3.5billion years ago when the first signs of modern-style microbes appear in the geological record.
Their assumption is that regardless of whether microbial life originated on Earth and possibly got blown to Mars during a major meteor impact, or vice-versa, if there are microbes growing in both environments now they'll be related.
I was going to say that you don't necessarily need specific bases for DNA amplification - there are some "whole genome amplification" techniques now that use a mix of small "random" primers to get amplification of (hopefully) most or all of the DNA in a sample rather than just one gene.
However, the description of the project does explicitly say they're planning to try to amplify 16s ribosomal DNA sequences, which are very handy for phylogenetic analysis of known terrestrial prokaryotes:
I'm a bit skeptical of the "universality" of "universal" primers, especially as to their usefulness after ~3,000,000,000 years of divergence. On the other hand, unlike some of the previous tests a positive result from this experiment would be very unambiguous if they can rule out contamination.
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yep, based on the single datapoint of earth life using DNA, it's reasonable to expect and look for ET DNA. However, after rolling a die once and getting 4 it would be similarly reasonable to expect subsequent rolls to also be 4.
Extrapolating based on a single datapoint is shaky at best. But without alternative substances to check for, DNA seems reasonable.
This reminds me of the old saying about when holding a hammer, everything looks like a nail.
I'm an individual! Just like everyone else!
Did anybody else who's dowloaded the high res pic notice the white plastic pill bottle just right of center, about 1/3 of the way up from the bottom?
You never really know how close to the edge you can go until you fall off.
(A) we're either the first, or basically it takes ~X amount of time (X being the age of the universe) for intellegent life to evolve and we can't see ET sending us signals because he hasn't evolved yet or he's sending them from 200k light years away as we speak and wont see them for a very long time.
(B) Signal loss is so huge in the vastness of space we just cant possibily detect ET's version of Eight is Enough and Electro Woman and Dyna Girl. Maybe it's a blessing...
Yes we could.
Once again, another BS color image from Mars.
Anyone who cares to, do this: Open the image in Gimp or Photoshop.
Look at the per-channel histograms. You will see that someone compressed the Blue and Green channels before posting the image.
To fix:
Normalize each channel individually so that 0-255 spans the full channel range.
The result? Mars as Opportunity actually photographed it.
Does NASA really think that we are so simple-minded that we would be too confused and disoriented to see a Mars without red sky?
Mir tut es leid, Menschen daß Einfältigfehlersuchenbaumfolgendenaffen sind.
There's no reason I can think of to think that the end result of any abiogenesis process has to be DNA as the replicating molecule.
Earth is an incredibly diverse planet, environmentally speaking. The fact that no living things on Earth are non-DNA based makes me think that DNA is indeed the most-efficient way to handle replication. In other words, it's likely to outcompete any alternatives in Earth-like environments that are capable of supporting life to begin with.
Everything from the extremophiles found in deep-sea thermal vents to the highest mammalian forms is DNA-based. It's reasonable to start with DNA-based assumptions when you look for life elsewhere, abandoning those assumptions only after they fail to pan out.
Dahlmann tightly grips the knife, which he may have no idea how to use, and steps out into the plain.