Finding life on Mars isn't easy.

While NASA's Curiosity rover found that Mars could have once supported life at some point in the distant past, scientists still haven't been able to detect a definitive sign that either single cellular or multi-cellular life once roamed the Red Planet. Proteins, genetical molecules like DNA or RNA, are a biological indication of life, present or past.. They are huge, complex molecules assembled to sustain life and its molecular processes and genetics."

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http://www.space.com/21969-how-to-find-life-mars-technology.html#sthash.aPqdSVNy.dpuf

Some scientists contend that signs of life were already found by the first American lander to touchdown on the Red Planet. Viking 1 — which landed on Mars in 1976 — performed a life-detection experiment on which many scientists agree it did not uncover life.

NASA's Viking probes were the first ever to successfully touch down on Mars in a powered landing. The Viking 1 lander set down in July 1976 and didn't go silent until November 1982. Viking 2 landed in September 1976 and kept working until April 1980, a big step performed by NASA.

Recently, some scientists expressed doubt about the first conclusions drawn from the first Martian missions. Some contend that it is possible that Viking 1 actually destroyed the organic matter. The spacecraft and its analytical instrument were designed to detect life or remnants of life with instruments  not sensitive enough (detection limit of 40 ppb CO2) to detect the organic molecules NASA exobiologists were looking for.

The researcher McKay, doesn't think Viking 1 found life on Mars. The surface of Mars is hit too much by radiation to preserve the integrity of complex organic molecules, like DNA and RNA, McKay said the Viking sample - gathered from the surface of the planet - would not have played host to any life affirming material. It seems from the results of the Mars Curiosity probe and from previous missions, as well as from laboratory experiments, radiation on the surface of Mars, together with perchlorate destroys (complex) organic molecules even into  the subsurface. He concluded that it is required to get below the level that radiation can reach," about 5 meters into the Martian soil, McKay estimates.

A new instrument

Although the instruments on the 2020 rover (to come) are expected to seek for signs of ancient life, another instrument currently under development would help search for life signs in the more recent past.  MIT researcher Chris Carr and a team of researchers are currently developing a biomarker seeking instrument. He bets that life on Mars is distantly related to life on Earth. The instrument analyzes Martian dirt to uncover genomic information left behind by micro-organisms which became extinct up to 1 million years ago. The tool should be able to detect signatures of DNA and RNA on Mars. McKay even broadens the scope of Carr's work.

Although strands of DNA and RNA are only detectable for about one million years on Earth, Martian bacterial genome information could last much longer because of the cool, dry environment on Mars. "The sort of processes that destroy evidence of life on Earth over time have not been operating on Mars and so there's a better chance that on Mars one might find something that's like a biomarker that's been there for billions of years. Hence the method doesn't necessarily preclude existing or past life," McKay said. "The distinction is not so important on Mars."

A biomarker for life on Mars?

Well, when one is looking for life on Mars, the distinction IS important. Ethylene production is known to originate from cultures of bacteria like Pseudomonas putida and Pseudomonas fluorescens among many other strands of bacteria. The highest ethylene production by bacterial cultures is reached under conditions of delayed aeration, i.e. when the culture is in soils and aeration decreases to 4%. Ethylene production rises immediately after the beginning of aeration. Under these conditions ethylene production by P. fluorescens increases 2–3 times. Samples of nonsterile garden soil even produces the highest amounts of ethylene under anaerobic conditions.

It seems that ethylene produced by bacteria in soils, is a very good candidate biomarker when measured at the sub ppb level to be a witness of active bacterial life on the planet Mars. The sensitivity of existing techniques is orders of magnitudes higher than those which were used to look for CO2 from oxidized rock, when looking for molecules of life, like DNA or other genetic material. Ethylene is a very simple molecule which can be detected in continuous mode at 0.01 ppb levels with a laser-acoustic technique.

In that respect, I have the impression that NASA scientists have been looking for life on Mars in the wrong haystack. The techniques formerly and even recently used, DO NOT discriminate between past or exisiting life on the planet. A vital difference, yes indeed.

Hence my question, is their life on Mars, when the right haystack is chosen and when ultrasensitive techniques are used to detect ethylene as a universally produced molecule of life by living bacterial strains in Martian soils, even under anaerobic conditions and like in the first billion years of bacterial evolution on our own planet Earth?

Keep me posted.