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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."
Actually, there are fairly good odds that alien life uses DNA in a similar way that we do.
Primarily because proteins/amino acids are the only chemical family that has the variation needed for life to function. Sugars don't have the variety necessary and lipids have difficulty interacting with aqueous environments. the 20 amino acids we use cover the full range of conditions, acid/base/hydrophobic/hydrophilic/big/small/odd (proline). It is unlikley that other lifeforms will use significantly more or less amino acids even if the specific chemistry is slightly different.
The biggest problem with proteins is that they can't store information. They can't form complements and unfolding a protein to directly read off the amino acid sequence typically destroys the original protein. Life needs a repository of information that is self correcting and is non-destructive to existing proteins.
Since sugars and amino acids are common (sugar forms easily and amino acids are necessary for efficient life) it is not unlikley that DNA/RNA (which is based off of these two molecular families) would form and it DOES fit the bill for data storage. Since simplicity provides stability, it is unlikley that a huge number of different base pairs would be used so either 2 or 4 bases are likley. Due to space limitations it is very unlikley that a DNA/RNA system would use more than 3 hydrogen bonds and 1 hydrogen bond is too weak. Therefore the list of usefull base pairs drops to either 2 or 3 bonds and we call them adenine, thymine, guanine and cytosine.
I freely admit that this is based off of an N of 1. But even with that said it is important to remember that life is hard and the simpiler/more efficient a system is the better able a life form is to survive. While the system we use isn't mandatory, it is very likley that it is representative of other similarly effective systems.
A PCR system would be able to detect the residue of a lifeform that looks even remotly like us on a molecular level. Since we know our system works and we have no knowledge of a different life system it is only reasonable to look for a system we know works. PCR is our best bet for identifying life.