Better Questions

From Rick Eyerdam

 I have just published a NASA history covering from NACA to the present days with the focus on NASA’s search for life in space, rather than the manned program. It is called: Exobiologists, Rocketeers and Engineers: Inside NASA’s Quest for Life in Space.

Because of the constraints of contemporary knowledge NASA searched incrementally for “life as we know it.” That was, of course, a moving target as science discovered far more robust and diverse life forms on earth than identified by our early exobiologists. They went to Mars searching for life while missing a third of the family tree.

In 1977, a year after the Viking mishap, Woese and Fox published these earthshaking words: Eubacteria and urkaryotes correspond approximately to the conventional categories "prokaryote" and "eukaryote" when they are used in a phylogenetic sense. However, they do not constitute a dichotomy; they do not collectively exhaust the class of living systems. There exists a third kingdom which, to date, is represented solely by the methanogenic bacteria, a relatively unknown class of anaerobes that possess a unique metabolism based on the reduction of carbon dioxide to methane (19-21). These "bacteria" appear to be no more related to typical bacteria than they are to eukaryotic cytoplasms. Although the two divisions of this kingdom appear as remote from one another as blue-green algae are from other eubacteria, they nevertheless correspond to the same biochemical phenotype. The apparent antiquity of the methanogenic phenotype plus the fact that it seems well suited to the type of environment presumed to exist on earth 3-4 billion years ago lead us tentatively to name this urkingdom the archaebacteria. Whether or not other biochemically distinct phenotypes exist in this kingdom is clearly an important question upon which may turn our concept of the nature and ancestry of the first prokaryotes.  (Balch WE, Magrum LJ, Fox GE, Wolfe RS, Woese CR.J Mol Evol.)

This realization cracked open the door to a search for life on Earth that acts different than we once suspected. But how wide should that door be opened?

 

I have begun the second book. It is Inside NASA’s search for life, Part 2. And its purpose is to focus on the questions raised by the first book.

 What is the definition of life that works 100% of the time? When will we have it? Who will decide? Why look for new life until this is decided?

 Can we sort through unknown organic molecules without the potential ambiguity inherent in pyrolization? Must we destroy molecules to understand their makeup?

 Are we sure that the difference between non-earthly and earthly life can be measured entirely by counting amino acids and determining chirality?

 Is the standard of 20 specific amino acids and left-handedness sufficient?

 Do we have a juried, consensus standard test for earthly life; a device that identifies the earthly amino acids and another device that establishes their chirality?

 What can we conclude if or when we discover life forms on earth that do not match the 20 amino acid standard or offer right-handed chirality? Do they extend the definition of life as we know it, because they have been found on earth? Or are they, by definition, life on earth from elsewhere in space and time? Who decides?

 I was able to structure my first book around the growth and embrace of the concept of chemical evolution and the very interesting people who advocated exobiology when there was no such thing, no lexicon and no laboratory. The exobiologists needed rockets to search for life and rockets required money and engineers. I focus on two engineers, one a mechanical engineer at Langley and the other a sanitary engineer invented a Mars life search experiment that worked. They are the heart and soul of the Viking life search mission.

 For the second book I must find a narrative structure that addresses the questions I want answered but in an interesting if not compelling way. So I have launched the Tardigrade Project as the scaffolding for the book.

 Once exposed to them, everyone loves the Tardigrades. They can be studied in the classroom and collected almost everywhere. What they do, however, challenges the definition of life as we know it. If life as we know it requires metabolism; ongoing biochemical life processes, growth, respiration, digestion, some Tardigrades don’t qualify while in their tun state. They die and from the miracle of water, they come back to life sufficiently to reproduce.

So I plan to pretend that a space ship brought back a sample of yuk from a crack on a meteor or down some water-filled lava tube on Mars. Within this yuk there was a Tardigrade tun. Scientists look at the tun and call it dead. But wait! Look it is forming a primitive body devoid of circulatory and respiratory systems and with a minimal excretory system. And then an egg emerges. So it is now alive. But is it life as we know it on earth? Does it meet the consensus tests for amino acids and chirality?

So we interrogate the space science system to test the Tardigrade and we are compelled to answer the questions listed above before we spend billions flying through moon ejecta or driving around Mars, drilling holes and hoping to stumble on a sample that can be safely returned for earthly study.

In my book I say, “The bad news is that no matter how much money NASA spends it can never know if life on Mars evolved on Mars, if we finally get there and if Mars life acts just like life on Earth. The good news is that there are two ways of knowing with some certainty that the galaxy is filled with life different from life on Earth. The first method requires far more words and science than many of us are prepared to consume. But it can be explained simply and tested with relative ease.

            Every living amino acid molecule we know of on Earth rotates in the same direction. Earthly living amino acid molecules are left-handed and cannot interact with right-handed molecules, though we know right handed molecules exist. If we ever find a living molecule on Mars and its amino acid is right-handed, we can be pretty sure, almost positive; it did not come from Earth. In that case, we can feel almost positive the universe is alive with a variety of life forms, some left handed and some right handed. The concept is called chirality and Levin proposed that experiment to NASA and Russia. Only the Russians were interested.

            The other absolute test for Earthly life is the one Francis Crick provided, before space flight, during his Nobel address back in 1961. Crick pointed out, “It now seems certain that the amino acid sequence of any protein is determined by the sequence of bases in some region of a particular nucleic acid molecule. Twenty different kinds of amino acid are commonly found in protein, and four main kinds of base occur in nucleic acid. The genetic code describes the way in which a sequence of twenty or more things is determined by a sequence of four things of a different type.”

            Crick continued, “It is hardly necessary to stress the biological importance of the problem. It seems likely that most if not all the genetic information in any organism is carried by nucleic acid - usually by DNA, although certain small viruses use RNA as their genetic material. It is probable that much of this information is used to determine the amino acid sequence of the proteins of that organism.”

            “It is one of the more striking generalizations of biochemistry - which surprisingly is hardly ever mentioned in the biochemical textbooks - that the twenty amino acids and the four bases, are, with minor reservations, the same throughout Nature,” Crick told the Nobel audience.

            And that is the second test. We will know we have life that is like life on Earth because Earthly life uses only the same twenty out of the thousands of amino acids plus the same four base pairs to retain and convey its genetic code. Find a life form with more or less than 20 amino acids and four base pairs and you have found yourself a genuine alien.

            So we should do more than just go to Mars to land technology or follow the water. We should save our money. We already know there is life on Mars. And the next time Earth men go to Mars, probably the Russians or the Indians or the Chinese, the robot should be trained to count amino acids and see if they are left-handed. There is no logical reason, other than hubris, to go to Mars if we cannot build experiments that can do just that perfectly, every time.

            The conclusion is similar to Bruce Murray’s worry when he and Carl Sagan were debating the merits of the Viking Mission back in 1972.

            “There are great hopes placed on the mission by American scientists,” Murray said. “But I personally continue to doubt that even as complex and expensive a robot as Viking is capable of carrying out so difficult a task as the unambiguous detection of life on a foreign planet by remote means.”

 Then it dawned on me to beat the drum steadily to answer the key questions on earth before we spend the money gathering samples in space and launching them into another fog of ambiguity. And the Tardigrade Project is my beginning.

 And here is the very cool part. I have a donor for Tardigrade samples and a major NASA astrobiology lab that expressed a willingness to run the tests but, once a committee meeting was held, decided that they are too busy now to take on the project. 

I have reached out to other labs and will keep you posted.