I’m Convinced We Found Evidence of Life on Mars in the 1970s

It looks like a lot of people think the presence of the oxidizer perchlorate is the cause of the false positive, but there isn't consensus yet.

```

On August 2008, the Phoenix lander detected perchlorate, a strong oxidizer when heated above 200 °C. This was initially thought to be the cause of a false positive LR result. However, results of experiments published in December 2010 propose that organic compounds "could have been present" in the soil analyzed by both Viking 1 and 2, since NASA's Phoenix lander in 2008 detected perchlorate, which can break down organic compounds. The study's authors found that perchlorate can destroy organics when heated and produce chloromethane and dichloromethane as byproduct, the identical chlorine compounds discovered by both Viking landers when they performed the same tests on Mars. Because perchlorate would have broken down any Martian organics, the question of whether or not Viking found organic compounds is still wide open, as alternative chemical and biological interpretations are possible.

...

In a paper published in December 2010, the scientists suggest that if organics were present, they would not have been detected because when the soil is heated to check for organics, perchlorate destroys them rapidly producing chloromethane and dichloromethane, which is what the Viking landers found. This team also notes that this is not a proof of life but it could make a difference in how scientists look for organic biosignatures in the future.

```[0]

It's funny that perchlorate is likely what confounded the LR experiment, as the discovery of perchlorate in the soil made a lot of folks less optimistic about life being able to survive on the Martian surface.[1]

[0] https://en.wikipedia.org/wiki/Viking_lander_biological_exper...

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5500590/

I get the feeling that contrary to rhetoric the search for life on Mars or anywhere else is almost an anti-priority. Not much designed to look for life has been sent since Viking in spite of direct observation of water ice, brine, and other features suggesting ideal landing sites for such experiments.

If perclorates were the cause of the Viking positive as many suggest, why not send a new experiment designed to rule that in or out? Why not send a whole lot more chemical tests for biology, or a microscope for that matter?

I suspect there is strong concern about the social effects of the revelation of any extraterrestrial life, even microbes. From what I see of the mass psychosis that is most of current political discourse this concern might not be unfounded.

> On July 30, 1976, the LR returned its initial results from Mars. Amazingly, they were positive. As the experiment progressed, a total of four positive results, supported by five varied controls, streamed down from the twin Viking spacecraft landed some 4,000 miles apart. The data curves signaled the detection of microbial respiration on the Red Planet. The curves from Mars were similar to those produced by LR tests of soils on Earth. It seemed we had answered that ultimate question.

This article does a poor job of explaining the experiment in question: "Labeled Release" (LR).

According to Wikipedia:

> ... In the LR experiment, a sample of Martian soil was inoculated with a drop of very dilute aqueous nutrient solution. The nutrients (7 molecules that were Miller-Urey products) were tagged with radioactive 14C. The air above the soil was monitored for the evolution of radioactive 14CO2 gas as evidence that microorganisms in the soil had metabolized one or more of the nutrients. Such a result was to be followed with the control part of the experiment as described for the PR below. The result was quite a surprise, considering the negative results of the first two tests, with a steady stream of radioactive gases being given off by the soil immediately following the first injection. The experiment was done by both Viking probes, the first using a sample from the surface exposed to sunlight and the second probe taking the sample from underneath a rock; both initial injections came back positive.[1] Subsequent injections a week later did not, however, elicit the same reaction, and according to a 1976 paper by Levin [author of the linked article] and Patricia Ann Straat the results were inconclusive.[12][13] In 1997, Levin, Straat and Barry DiGregorio co-authored a book on the issue, titled Mars: The Living Planet.

https://en.wikipedia.org/wiki/Viking_lander_biological_exper...

To recap, martian soil was incubated with small organic molecules bearing a radioactive label. A chemical process that converted them into CO2 would give off some radioactive gas. The gas was detected by both landers the first time the experiment was run, but not the second time.

It should be kept in mind that non-biological processes can also convert small organic molecules into CO2. Simple combustion will do this, for example.

This possibility is discussed later in the Wikipedia article (but not in the linked article):

> Despite the positive result from the Labeled Release experiment, a general assessment is that the results seen in the four experiments are best explained by oxidative chemical reactions with the Martian soil. One of the current conclusions is that the Martian soil, being continuously exposed to UV light from the Sun (Mars has no protective ozone layer), has built up a thin layer of a very strong oxidant. A sufficiently strong oxidizing molecule would react with the added water to produce oxygen and hydrogen, and with the nutrients to produce carbon dioxide (CO2).

However, this does not explain the discrepancy between the first and second test. And it leaves open the question of why both landers' experiments gave the same odd result (first test positive, second test negative).

The small organic molecules used as nutrients were those produced in a famous lab simulation of early earth. Its results showed that many of the basic building blocks of life could be formed by passing an electrical current through gases thought to be present in the early Earth atmosphere.

I don't think Levin is making the claim that NASA knows that there is life on Mars and that there is a conspiracy to cover it up. They both are looking at the same results and (honestly) coming to different conclusions.

Part of this is that it's expensive to do experiments on Mars, and space is limited. Each experiment you choose to do excludes you from doing others, so NASA has evaluated the evidence and doesn't think its the most efficient thing to pursue right now. Levin is trying to convince folks that the evidence is sufficient to warrant pursuing further experiments that would clarify what is going on here.

I think it's the opposite. There are scientists who are obsessed with finding extraterrestrial life because of their philosophical views regarding man's place in the universe. The fact that our universe seems primed for life has bothered so many gung ho atheistic scientists that they've conjured all sorts of semi-pseudoscientific multiverse theories (Sean Carroll). That's one part of it. The second part it's reducing abiogenesis to a simple process that just "takes time" and is almost inevitable. The goal is to try to shove bare faced facts into a dusty drawer while you trot out the latest sensational theory. This is why there's been constant attacks on the Big Bang theory even though it's one of the triumphs of modern cosmological science. It all becomes so easy to justify when you define science as "what atheists believe."