A Place to Stand

   The way to test a scientific theory is to get the evidence. Those who tell you "the debate is over" or there is a greater consensus than over the law of gravity (as Al Gore and the BBC said respectively of global warming) are frauds and charlatans, with no place in any scientific matter.

  So what sort of evidence would prove or disprove microbial life in space as discussed previously? Nothing but finding it could prove it and nothing but looking and failing to find it repeatedly could disprove it.

   I suggest 2 particular places. On a comet and Mars' upper atmosphere.

Searching a Comet

Actually a comet close approach, though not a landing has been made.

NASA's Stardust Mission launched a spacecraft, named Stardust, on February 7, 1999. It flew by Wild 2 on January 2, 2004, and collected particle samples from the comet's coma, which were returned to Earth along with interstellar dust it collected during the journey. 72 close-up shots were taken of Wild 2 by Stardust.

Stardust's "sample return canister," was reported to be in excellent condition when it landed in Utah, on January 15, 2006. A NASA team analyzed the particle capture cells and removed individual grains of comet and interstellar dust, then sent them to about 150 scientists around the globe. NASA is collaborating with The Planetary Society who will run a project called "Stardust@Home", using volunteers to help locate particles on the Stardust Interstellar Dust Collector (SIDC).


As of 2006,[11] the composition of the dust has contained a wide range of organic compounds, including two that contain biologically usable nitrogen. Indigenous aliphatic hydrocarbons were found with longer chain lengths than those observed in the diffuse interstellar medium.


In April 2011, scientists from the University of Arizona discovered evidence for the presence of liquid water. They have found iron and copper sulfide minerals that must have formed in the presence of water. The discovery shatters the existing paradigm that comets never get warm enough to melt their icy bulk.

   Proof of liquid water is certainly an amazing matter & does greatly enhance the habitability of the cometary cloud. On the other hand they didn't actually find living particles. On the 3rd and 4th hands not landing and only examining coma particles does limit the possibilities, the mission wasn't preconfigured to find life, or rather dessicated particles capable of life, and with the material spread around 150 scientists across life rich Earth it is difficult to think anything could have been found which could not have been considered contamination. As Professor Wickramasinghe said

The 2005 Deep Impact mission to Comet Tempel 1 discovered a mixture of organic and clay particles inside the comet. One theory for the origins of life proposes that clay particles acted as a catalyst, converting simple organic molecules into more complex structures. The 2004 Stardust Mission to Comet Wild 2 found a range of complex hydrocarbon molecules - potential building blocks for life.

The Cardiff team suggests that radioactive elements can keep water in liquid form in comet interiors for millions of years, making them potentially ideal "incubators" for early life. They also point out that the billions of comets in our solar system and across the galaxy contain far more clay than the early Earth did. The researchers calculate the odds of life starting on Earth rather than inside a comet at one trillion trillion (10 to the power of 24) to one against.

Professor Wickramasinghe said: "The findings of the comet missions, which surprised many, strengthen the argument for panspermia. We now have a mechanism for how it could have happened. All the necessary elements - clay, organic molecules and water - are there. The longer time scale and the greater mass of comets make it overwhelmingly more likely that life began in space than on earth."

  So lets send one, or better several, new probes to comets. The Stardust probe cost NASA $300 million (£190m) but with SpaceX having cut costs 20 fold and miniaturisation & other technology having also proceeded since then a 20 fold reduction in costs is reasonable. Particularly if the contract is given to the lowest commercial bidder. I suggest a 2 part process. Government should offer the money for a vehicle able to soft land a package of agreed size on a comet agreed to look a good candidate and universities & other organisations should compete to be chosen to have their instrument package landed. Cannibalising my previous asteroid prize motion

the Scottish Parliament to offer a prize of 15 million pounds to the first Scottish group to soft land a vehicle on an agreed comet, carrying a nominated package of ? kg in a condition to deploy.

  Or the British, or US, or Texan or New Mexican or Singaporean or wherever. Finding proof that life is spread across the universe is certainly something not beneath the most ambitious nation.

Searching Mars
But this is a new idea all my own. If Wickramasinghe's balloon experiment have found microbial life in Earth's upper atmosphere which did not come from Earth's surface then there should be comparable amounts of life in Mars' upper atmosphere. The presumed lack of such life on the ground, at least in common amounts, would be irrelevant if it didn't come from there and if Mars is close to as habitable as Antarctica on the surface its upper atmosphere would be a good a home to life as Earth's. But life found in the upper atmosphere would be proof of panspermia, whether it came from space or the surface or both.

    Sending a probe to dive through the tenuous upper atmosphere of Mars would be much easier than making a soft landing like Beagle. Such a probe could even return samples to Earth or perhaps Earth orbit where anything found could not credibly be put down to contamination with Earth's biosphere.

   When the Viking Lander first tested for life it was declared not to have been found because only 1 of the 4 experiments produced positive results. While the results haven't changed conclusions, for many, have.

Of the four experiments, only the Labeled Release (LR) experiment returned a positive result, showing increased 14CO2 production on first exposure of soil to water and nutrients. All scientists agree on two points from the Viking missions: that radiolabeled 14CO2 was evolved in the Labeled Release experiment, and that the GC-MS detected no organic molecules. However, there are vastly different interpretations of what those results imply.

The image taken by Viking probes resembling a human face caused many to speculate that it was the work of an extraterrestrial civilization.One of the designers of the Labeled Release experiment, Gilbert Levin, believes his results are a definitive diagnostic for life on Mars. However, this result is disputed by many scientists, who argue that superoxidant chemicals in the soil could have produced this effect without life being present. An almost general consensus discarded the Labeled Release data as evidence of life, because the gas chromatograph & mass spectrometer, designed to identify natural organic matter, did not detect organic molecules.The results of the Viking mission concerning life are considered by the general expert community, at best, as inconclusive.

  I find "inconclusive" hard to argue with but since the same Viking experiment carried out in Antarctica also failed to find life there it is reasonable to assume the fault lies more in the experiment than in life not actually being there.
    More recent observations have found both methane and formaldehyde in the Martian atmosphere.

Trace amounts of methane in the atmosphere of Mars were discovered in 2003 and verified in 2004. As methane is an unstable gas, its presence indicates that there must be an active source on the planet in order to keep such levels in the atmosphere. It is estimated that Mars must produce 270 ton/year of methane, but asteroid impacts account for only 0.8% of the total methane production. Although geologic sources of methane such as serpentinization are possible, the lack of current volcanism, hydrothermal activity or hotspots are not favorable for geologic methane....

Mars Express Orbiter, detected traces of formaldehyde in the atmosphere of Mars. Vittorio Formisano, the director of the PFS, has speculated that the formaldehyde could be the byproduct of the oxidation of methane, and according to him, would provide evidence that Mars is either extremely geologically active, or harbouring colonies of microbial life   Again not conclusive but that is, again, quite a lot of evidence piling up that life is indeed tenacious enough to be there. If I were betting I would bet on it being there but the only way we will know for sure is by going and looking.
 
   Finding life beyond Earth means we are not alone in the universe (though it may not mean there is other intelligence). That would be one of the most important things in human history and well worth 0.0002%  of annual human wealth (£100m or 1 minutes worth).
 
   The philosophical aspects bear study.