Prime Time Replay:
Ken Nealson
on looking for lifeforms on other worlds
MsgId: *breakthrough(1)
Date: Wed Sep 10 20:57:56 EDT 1997
From: moderator At: 152.163.194.21
Hi, I'm your moderator, Madeleine Lebwohl, and tonight I'll be speaking with Ken Nealson. Welcome, Ken!
MsgId: *breakthrough(2)
Date: Wed Sep 10 20:59:39 EDT 1997
From: kennealson At: 137.78.77.133
Hi Madeline
MsgId: *breakthrough(3)
Date: Wed Sep 10 21:01:21 EDT 1997
From: moderator At: 152.163.194.21
Ken, tonight I understand you're at the Jet Propulsion Laboratory at Cal Tech. Could we talk a little about the project you've begun?
MsgId: *breakthrough(5)
Date: Wed Sep 10 21:04:19 EDT 1997
From: kennealson At: 137.78.77.133
Sure -- I have been recently hired by JPL (Cal Tech) to set up a group in Astrobiology. Astrobiology can be defined as the study of almost everything!! We have some foci, however, as we are setting up a group consisiting of environmental microbiologists and geochemists. Our goals are to study extreme environments and organisms that live in these environments in order to try to plan experiments to detect life in similar or more-extreme environments on non-Earth habitats.
MsgId: *breakthrough(7)
Date: Wed Sep 10 21:08:41 EDT 1997
From: moderator At: 152.163.194.21
So you've had to pick organisms on earth that you hope will resemble those on other planets? Which ones are you studying?
MsgId: *breakthrough(8)
Date: Wed Sep 10 21:11:36 EDT 1997
From: kennealson At: 137.78.77.133
That's a good question. It will depend on where we consider studying -- which non-Earth environment. Also, on each planet there will be a variety of different environments, some of which may have connections to Earth. Let me enlarge on that -- Mars is very cold, dry and irradiation rich on the surface. We know of nothing like it on Earth. However, it is conceiveable that under the surface the groundwater is melted and there are reasonably hospitable places.So, if we look at Atarctic environments which are cold and dry, but have episodic inputs of water via melting, we may find abundant organisms that could be similar to organisms that could exist on similar places on Mars. Also, if we deep in the interior of the earth, we find abundant bacteria growing on hydrogen given off by the rocks -- similar enviornments could easily exit on Mars, but we would only find them by drilling. Such thinking goes on and on.
MsgId: *breakthrough(10)
Date: Wed Sep 10 21:14:16 EDT 1997
From: moderator At: 152.163.194.21
How did you decide what might be on Mars? Have you used information from the Martian meteorites on earth?
MsgId: *breakthrough(11)
Date: Wed Sep 10 21:18:12 EDT 1997
From: kennealson At: 137.78.77.133
Most of what we know about Mars comes from the Viking experiments of the 1970s. These experiments included two landers and two orbiters that did some fairly good chemistry and meteorology of the planet, characterizing much of the surface by remote sensing, and collecting data from the landers. This information showed the harshness of the surface, indicated that no water was presently on the surface, did some preliminary mineralogy, and showed the distribution of impact craters and volcanic remnants. The Mars meteorites have been somewhat helpful, especially in terms of mineralogy, as they have been possible to study in great detail. So from small samples we have learned a lot about the detailed properties of the surface.
MsgId: *breakthrough(12)
Date: Wed Sep 10 21:20:32 EDT 1997
From: moderator At: 152.163.194.21
Were there indications of bacteria? And what are you looking for when you explore for ancient signs of life?
MsgId: *breakthrough(13)
Date: Wed Sep 10 21:24:05 EDT 1997
From: kennealson At: 137.78.77.133
There have been presumptive indications of bacteria reported on one of the Mars Meteorites (ALH84001), but these are not confirmed as bacteria, and do not represent the best way to look for life. In fact one of the major issues our group is wrestling with is the whole issue of how one defines life, and how it can be sleuthed out of an environment that is apparently lifeless. This includes both ancient parts of the Earth (long dead rocks) and samples from extraterrestrial sources. The best fossils are probably chemical fossils that would occur only if life is or was around. Let me give you and example.One of the major tools of biological sleuthing is that of looking for fossils, but with bacteria, these fossils are so small as to be easily confused with other things. Thus we use other indicators of life as our tools. A good example is the use of stable isotopes. Many elements have more than one isotope, some of which are radioactive because they decay to give other products plus radioactivity. However, others are stable, and do not decay, but have different molecular weights. For instance, carbon has three major isotopes. Carbon 12, which is most of the carbon, carbon 14, which is radioactive and unstable, and carbon 13, which is stable. When enzymes see C-13, they react with it more slowly than they do C-14. Thus living organisms tend to be "lighter" isotopically than non-living sources of carbon. It is this geochemical lightness that we use as an indicator of life in the past. It can be very diagnostic. One can make an analogy here to throwing balls over a wall. If there are occasionally heavy balls, they will end up being tossed over at a slower rate. Enzymes have the same tendency, so living carbon is light. In a similar way, isotopes of sulfur and nitrogen tend to accumulate in living material as the lighter forms. Another indicator of life might be complex molecules that occur in abundance which would simply not be predicted to be present and stable in abiotic enviornments.
MsgId: *breakthrough(17)
Date: Wed Sep 10 21:45:29 EDT 1997
From: moderator At: 152.163.194.21
Did you find anything in the martian samples that seemed to indicate traces of life? Is this a project in which you really expect to find traces of life, or is it more of an experimental one.
MsgId: *breakthrough(18)
Date: Wed Sep 10 21:50:15 EDT 1997
From: kennealson At: 137.78.77.133
So far, nothing has been found by our group to indicate life, but as with the group that reported on the Mars meteorite last year, nothing has been found to be inconsistent with it. Thus the jury must be regarded as still deliberating. One might look to pathfinder and sojourner for some help, but little convincing evidence has appeared yet. So far no minerals or isotopes indicative of life have been seen, although it should be stressed that the surface of Mars is so hostile that very few believe that any life could be found there.Tomorrow, the Mars Global Observer will begin gathering remote sensing data of the planet for the first time in more than 20 years, and with these new sensors we may learn a lot of very critical things about the planet. They may be much more definitive, or just lead us to new questions.
MsgId: *breakthrough(19)
Date: Wed Sep 10 21:51:24 EDT 1997
From: moderator At: 152.163.194.21
Do you have a wish list for what it might find?
MsgId: *breakthrough(20)
Date: Wed Sep 10 21:54:37 EDT 1997
From: kennealson At: 137.78.77.133
Sure do. As with the Earth, one might hope to find that there are "hot spots" near the surface -- places like Yellowstone or Iceland, where the crust is thin and the magma of the hot core comes close to the surface. This would be a place where more hospitable environments might exist close to the surface and where the search for life, either present or past, might be much more fruitful. I regard these remote sensing missions as key to the search for life, as they will give us critical hints as to where to go with the next surface missions, and especially with the sample return expedition(s).
MsgId: *breakthrough(21)
Date: Wed Sep 10 21:57:01 EDT 1997
From: moderator At: 152.163.194.21
Is there any possibility that there are surprises waiting in the samples from Mars? Any inconsistencies in the rocks you've looked at that hint at something new? Even on earth scientists keep finding life in places where they thought it couldn't exist. Could Mars have something never seen before?
MsgId: *breakthrough(22)
Date: Wed Sep 10 21:59:48 EDT 1997
From: kennealson At: 137.78.77.133
There is no reason to expect anything one way or another, but the recent finding of life in environments where it was considered to be impossible just a few years ago leads one to the notion that life is considerably more tolerant to extremes than we had thought. Given this, the surprise has already occurred, and now we need to go to environments on Mars where conditions may approach those of the most hostile on Earth and see if life is as resilient in these places. It is a long shot, but with an immense pay-off no matter what the answer is.
MsgId: *breakthrough(23)
Date: Wed Sep 10 22:02:32 EDT 1997
From: moderator At: 152.163.194.21
What are some of the payoffs? Besides the obvious -- what an incredible discovery -- what are there questions here that Mars would answer?
MsgId: *breakthrough(24)
Date: Wed Sep 10 22:11:34 EDT 1997
From: kennealson At: 137.78.77.133
Sorry, I got disconnected again. That is a good question. The payoffs are potentially great due to two things that may be lacking on Mars. The first, of course if life -- if Mars has no life, then it will not recycle, and because of lifes need to recycle, most of the past history of the planet Earth does not exist. Recycling of the elements is akin to survival of life, so most of the life gets consumed by the survivors and next generations. This leaves little of our history to use to try to understand the past. Furthermore, most of our records of past history have been destroyed by metamorphosis of rocks, a result of plate tectonics on the planet. Mars has no plate tectonics, so if past history of life, or even prebiotic chemistry was ever there, it may still exist, an exciting thought. It would be an ironic twist if by searching for life on Mars we discovered key things about our own origins by studying prebiotic chemistry of a dead planet!
MsgId: *breakthrough(26)
Date: Wed Sep 10 22:19:17 EDT 1997
From: moderator At: 152.163.194.21
Is there any concern that what we see as dead might not be dead -- that something unknown might come back? Is there any concern about how our earliest forms of life might react if they were suddenly mixed with life as it is now?
MsgId: *breakthrough(27)
Date: Wed Sep 10 22:19:58 EDT 1997
From: kennealson At: 137.78.77.133
You asked me what my role in all of this is? I feel that my involvement will be at several levels, but if I had to say where I think the most exciting information will be, and where I would like to be involved, it will be with sample return issues. For example, when we can bring back specific types of rocks and minerals, and examine them in great detail on Earth, I think we will have a much better understanding of the history of the planet, its past, and the role, if any, of life in the history of the planet. That will be an inspiring bit of scientific work, and I hope that our Astrobiology group can play a part in it. Given the time constraints of such missions, that is probably more than enough to hope for.That's all for now! Ken Nealson
MsgId: *breakthrough(29)
Date: Wed Sep 10 22:24:36 EDT 1997
From: moderator At: 152.163.194.21
Good luck on receiving your new data from Mars! Thanks for joining me. Goodnight.Please join me next week when I speak with Dr. Bruce Perry, of the CIVITAS Child Trauma Programs in Houston, Texas.
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