The following is a summary of most of the talks and activities associated with the Bioastronomy 2002: Life Among the Stars conference. This conference continues a succession of meetings organized by the IAU Commission 51 (Bioastronomy). The objective is to review progress in all fields of bioastronomy (also known as astrobiology). (Interested readers may also want to consult my summary of Bioastronomy 2004: Habitable Worlds.)
A caveat is in order. I am not an expert in many of these fields. I have recorded what I understood the speaker's main points to be. In some places I have added interpretation or questions. However, any errors in this document almost certainly reflect my lack of understanding of a field and caution should be used in order that a speaker's remarks are not overinterpreted based on what I recorded. In addition to differing levels of understanding, the talks were of differing length. Thus, the length of my notes from speaker to speaker reflects many factors. Finally, I (rightly or wrongly) took no notes on the posters. Thus, there are a number of presentations not recorded here.
(Also, I have used a fair amount of jargon or specific terms at various points in this summary. Given time constraints I may be willing and able to explain what various terms mean if asked.)
The conference opened with a talk by Harrison Schmidt, the only scientist to have walked on the Moon. His training is geology. (He was accompanied to the stage by a Hamilton Island buggy made up to look like a lunar rover.) There must have been some context that I was missing because in places he seemed to be suggesting that the conventional theory for the origin of the Moon was incorrect. He never really came out and said this or if he did he didn't provide any simple listing of the problems with the conventional theory. He did mention that chrondritic material had been recovered from deep within the Moon, which he seemed to suggest would have been inconsistent with an impact origin. He also commented that there is some evidence for a magnetic field in the Moon roughly 3.9 Gyr ago. (In conversations with others later, their impressions were that he was suggesting definitely that the impact origin model is wrong. He prefers a separate accretion origin for the Moon followed by an impact-assisted capture in which the impact dissipates the angular momentum so that the Moon can be captured by the Earth.)
The next talk was a welcoming talk by Baruch Blumberg, who has won the Nobel Prize in Medicine for his development of the hepatitis B vaccine. He is now director of the NASA Astrobiological Institute. His most notable comment was a comparison between the astrobiological enterprise and the building of cathedrals in medieval Europe. Namely, he thinks that the search for life in the Universe and the effort to understand its origin and distribution may be a multi-generational project. I'm not sure if that is a welcome comparison or not. Much of science is multi-generational. For instance, modern cosmology can be said to have started in either 1915 or 1930. Either way, it has taken approximately 80 yr to get to our current understanding, and it will be another decade (at least) before we have resolved some remaining uncertainties.
Chris Tinney summarized planet hunting. His contributions were twofold. First, he emphasized to all speakers that the audience is a mix of astronomers, biologists, etc. so that jargon may be problematic. He distributed yellow cards with the instructions to audience members that they should wave their yellow cards if he (or following speakers) resorted to an unfamiliar word. He also summarized what we know about the second term in the Drake equation:
~ 0.85% of Sun-type stars (G) have hot Jupiters;
~ 7--10% of Sun-type stars have a gas giant with an eccentricity e > 0 within 3 AU;
~ 1% have gas giants between 0.15 AU and 3 AU with e ~ 0; and
~ 50% of the stars with planets have multiple planets when the radial velocity curves are sampled densely enough.
Jill Tarter summarized the reasons for looking at centimeter wavelengths for SETI (although she did not mention the fact that cm-wavelength radiation can propagate across the Galaxy). She then summarized some of the reasons that folks are looking increasingly toward optical SETI. She also seems to think that there is little danger of everybody looking and nobody transmitting because as civilizations "mature" they would likely begin transmitting. (I'm not sure I agree, though, with her definition of "mature." She seems to conflate reaching a stable technological plateau [rather than blowing up or poisoning themselves after a short time] with increasing compassion or "higher qualities.")
Bailey summarized the chirality issue within bioastronomy. Biological molecules are chiral; in the case of terrestrial life, it uses the L form of molecules. What is the origin of this chirality? Three possibilities discussed: chance, the weak interaction, or polarized UV light. People tend to favor polarized UV light because the weak interaction is weak, and it is difficult to investigate chance. Moreover, this entiomeric excess of L molecules is apparently quite general, existing in amino acids found in the Murchison meteorite. Thus, an astrophysical origin seems plausible. He was dismissive of circularly polarized light from neutron stars as being the origin of chirality favoring an origin from polarized light in star forming regions. Circularly polarized light will destroy either L or R chiral molecules preferentially, depending upon whether the circularly polarized light is right or left circularly polarized. However, the amount of molecules destroyed in order to produce a reasonable excess is excessive. For instance, 99.98% of all molecules have to be destroyed in order for the remainder to have a 15% entiomeric excess. He suggests that perhaps circularly polarized light destroys a precursor to biological molecules.
Flynn studied interplanetary dust particles (IDPs), claiming that carbonaceous chrondite meteorites are bad case studies because they have been heated too much. He finds/argues that IDPs contain organic material which means that it would have formed prior to the formation of asteroids.
Sun Kwok is finding complex organic ring and chain molecules (e.g., benzene) in AGB environments. In response to my question, he favors IR not mm-wave observations because it is easier to distinguish the molecules in the IR.
Whittet claims that interstellar dust grains contain a large fraction of biological elements, like C, O, N, etc. He showed that clouds with an embedded star have much richer spectra than clouds illuminated by background stars. Moreover, clouds with high-mass stars embedded have richer spectra than clouds with low-mass stars implying that the chemistry is driven by the UV light from the high-mass stars. Not clear to if there is a transport problem. Do the chemical products formed in high-mass stellar environments survive to be incorporated in the planets of low-mass stars?
Bishun Khare is investigating C nanotubes, chains or rings of C about 1--10 nm in diameter and 10 microns in length. Actually may be similar to soot particles, but I'm not clear how they form in interstellar space. He also favors a PAH origin for the ubiquitous 3.4 micron spectral feature.
Ruiterkamp argues that many of these biological or organic molecules in space require considerable amounts of shielding to survive. Also he is involved in an experiment to put PAHs on the International Space Station for long-duration flights to see what happens to them.
Sutton described mm-wave studies of (interstellar?) organic molecules, but it wasn't clear to me how they selected the particular molecules to study that they did. He argued that one can use methanol maser emission to help understand systematics and derive total abundances of these molecules without recourse to CO observations and possible opacity concerns.
Geoff Marcy summarized planet search results, with an emphasis on the work by his group. His numbers were similar to those of Chris Tinney. Among their various results are that they are getting down to detecting 40--60 Earth-mass planets. He hopes to get down to 20 Earth-mass planets, but doesn't foresee being able to do much better than that. He discussed 55 Cnc at length, in part because the third planet in the system has an orbital period suspiciously close to the rotation period of the star itself (~ 40 d). There is some concern that the third planet might not be real, but an effect from a stellar spot or something similar. They are finding lots of resonances, which is consistent with the notion of orbital migration. He noted that some classes of planets are missing, notably massive planets close to the host star (most planets within 0.1 AU or so tend to be less than 1 Jovian mass) and large eccentricity, massive planets. This might indicate something about the efficiency of orbital migration for massive planets, either it is extremely efficient and the planet cannot stop from plunging into the star or it is extremely inefficient and the planet never starts migrating.
Charles Beichman gave a sales pitch for TPF, which is driven primarily by angular resolution. In order to see a planet in the habitable zone of a nearby main requires an angular resolution better than 100 mas. He did, however, have a humorous summary of the 18th century effort to observe the transit of Venus. The British Royal Society established a committee to study the idea, wrote a proposal to King George using elements we still use today (competition with other nations), and estimated a budget that was too low by a factor of pi. On that voyage of the Endeavour, Capt. James Cook encountered the Whitsunday Islands and the Great Barrier Reef. He liked the former but described the latter as an "insane labyrinth."
Neill Reid described efforts to measure the metallicity of stars with planets. Previous efforts have suggested that stars with planets have higher than solar metallicity. Reid criticized these efforts as not having paid sufficient attention to selection effects. Using what he claims is a more homogeneous sample, he finds that there is a trend of increasing metallicity meaning that a star is more likely to have a planet, but the magnitude of the effect is small. He also notes that stars with planets have "cooler" kinematics (they tend to be younger) and argues that he finds no trend of metallicity trend with spectral type (i.e., depth of convective zone) as one might expect if pollution were responsible for metallicity.
Caldwell described a transit experiment in Antarctica, and Ray Jayawardhana described a direct detection experiment with Keck.
My talk went over well. A couple of people asked astute questions, and I've received a number of comments since that people liked and understood my talk.
Selsis asked whether the faint Sun paradox may be even more problematic because the abundance of CO2 would have been lower in the past so the greenhouse effect would have been less. He suggests CH4 would have provided additional greenhouse warming. However, as O2 levels began to rise about 2 Gyr ago, this would have created a negative feedback loop in which O2 oxidized the CH4 and shut down the greenhouse effect. He suggested that the timing of the "snowball Earth" episodes about 2 Gyr ago and the rise of O2 were linked to the depletion of CH4 in the atmosphere. An audience member pointed out that reduced (i.e., not oxidized) sediments about 2.8 to 2.2 Gyr ago are consistent with high CH4 abundance (i.e., reducing) in the atmosphere.
Penny Sackett described gravitational microlensing searches for planets. The program has been going on for 5 yr, with 43 well-sampled light curves. Thus far no planets have been detected. The results depend on upon the trajectories, but the upper limits are that less than 50% of the Galactic stars have a Jupiter (1 Jovian mass at 5 AU). (In the conference summary, Ron Ekers pointed out that Sackett's microlensing studies had helped rule out a prior claim of a detection of an Earth-mass planet.)
Charles Lineweaver used a simple completeness correction to the known planets. He then applies the completeness correction to the (currently) poorly sampled part of the mass-period plane that contains Jupiter. He concludes that Jupiter is usual.
Sparks is looking at A Centauri, Gl 229B, and dust disks with the new HST camera.
Jack Welch has detected a "companion" in 1 mm observations of HL Tau, a 5\sigma enhancement in a disk around HL Tau. Its spectrum is (wavelength)-2.5, which is consistent with grain growth occurring. His speculation is that this is a disk instability, as some planetary formation models predict.
Meadows lays out a roadmap for characterizing terrestrial planets via their spectra. Lots of work to be done, only at the start. The intent is to use the spectra both to guide and interpret future missions. There are five steps: radiative transfer + climate modelling + atmospheric chemistry + exogenic and geological process + biology. The idea is to look at Venus, Earth, Mars, and Early Earth. One early conclusion is that ozone may not be a good biomarker.
Walter described analysis of an Australian orebody, at Here's Your Chance (HYC). This is apparently the result of an ancient hot springs, which deposited considerable Pb, Zn, and Au. The estimated age is 1.64 Gyr. He has found microfossils and organic compounds in the orebody. He suggests that orebodies or similar hot springs remains would be a place to consider looking on Mars.
Chris Chyba reviewed the search for life in the solar system. He suggests that, by analogy to water, we will only have a theory of life once we have multiple examples of it. Water could not have been described uniquely until the molecular theory was developed. Similarly, until we have multiple copies of life we will not have enough knowledge about life to make a "theory" of it. Thus, not having any other guide, he will restrict the search to life as we know it, namely something that makes use of our biogenic elements (C, O, N, etc.), water, and free energy. He commented briefly on C-based life versus other forms; the most popular suggestion is Si. While he doesn't rule it out, he notes that interstellar chemistry is rich in C-based molecules but not so with Si-based molecules. He also commented briefly on how meteorites containing organic molecules contain only simple monomers. He implied that this might have implications for the origin of life in the deep Earth. In the search for life, he described Mars Odyssey results. It carries a neutron detector and gamma-ray detector. Cosmic rays hitting the surface produce high-energy neutrons, which can be scattered to lower energies by hydrogen. Moreover, the neutrons can hit the hydrogen to produce deuterium, which can emit a 2.2 MeV gamma-ray. Thus, a deficit of neutrons and emission of 2.2 MeV gamma radiation is interpreted as indicating the presence of hydrogen and, because the most cosmically abundant molecule containing hydrogen is water, by inference water. Large deposits of water have been found on Mars, suggesting places to look for life. However, he also noted that the search for life on Mars may be complicated by the transfer of biogenic material via meteorites. If life on Mars is found, we may not learn a lot. He then switched to Europa and summarized the evidence for an ocean under Europa's surface. The evidence for an ocean on Europa consists of its density which requires a fair amount of icy materials, the tidal heating input, the appearance of apparently frozen ice floes on the surface, the relative young age of the surface, and the induced magnetic field. Combined these all suggest a sub-surface ocean, perhaps 100 km thick with a total volume about twice that of the Earth's oceans. Coincidentally, estimates are that the salinity of this ocean would be comparable to that of the Earth's oceans, which may be problematic for the formation of cells as that may hinder their formation. He described recent work in which estimates of the radiation-induced chemistry on the surface of Europa may provide a sufficient amount of "food" for any oceanic life. He also stressed that boring into the ice sheet may not be necessary to demonstrate life on Europa. If there is circulation of the ice or upwellings of water, there may be extremely young surfaces that could be examined for the presence of remnants of life. He also asked whether Europa forms a good model for the Early Earth, which may have been frozen over because of the faint Sun. During the discussion experiment, an audience member pointed out that Jupiter would have been more luminous in the past. He acknowledged that might mean that Europa's ice crust was thinner in the past, potentially thin enough that solar energy could serve as an additional source of energy for the origin of life. In response to a question from Heather Couper, he acknowledged that the Viking labelled-release experiment would not have been sensitive to low levels of bacteria in the Martian soil, at the level of 105 g/cm3. However, he also pointed out that much of the criticism leveled at the conventional interpretation of the Viking labelled-release experiment has not been in the peer-reviewed literature. Couper even used the word "rumor" in her question, and Chyba commented that he finds it difficult to respond to rumors. (I asked him later about the tidal heating input to Europa and whether it is large enough to produce hydrothermal vents at the ocean floor. He said that, depending upon how one estimates the tidal heating input, there may be hydrothermal vents, but the uncertainty on the estimates are large enough that such a conclusion is uncertain.)
Evertt Gibson described analysis of ALH840001. The meteorite contains carbonites, which contain magnetites. He compared the magnetites from ALH84001 to MV-1, a terrestrial sample of biogenic magnetites. He concludes that the two are so similar that the ALH84001 magnetites must have been formed biogenically.
Gilmour described PAHs in meteorites. He found a trend of decreasing 13C with an increasing number of C atoms. He argues that this requires a low temperature environment. He argues further that the meteorite precursor and the organic material within must have formed in an aqueous environment. He suggested clays.
Keller described observations of KBOs. Observed ones are diameters between 40 and 100 km; those of order 100 km must have had nuclear decay within their interiors, which would have modified the constituents. The number density of KBOs is so high that they must have been modified collisionally. He also suggests looking at IR spectra of circumstellar dust disks. They appear to have spectra similar to that of Comet Hale-Bopp, suggesting that there may be large numbers of KBOs in these dust disks.
Marov argued that a large fraction of Earth's volatiles are due to comets, because they could have delivered a volume comparable to that of the Earth's oceans.
Pierazzo discussed impacts, pointing out that they can be quite destructive but also important for the evolution and distribution of life. The destructive influence of impacts depends upon their magnitude, duration, and abruptness. (I realized later: What about frequency?) She described short-term influences as global wildfires and climate perturbations whereas long-term influences include acid rain and greenhouse effect increases (or decreases). However, the long-term influences may depend upon the composition of the impactor and the material impacted. She is trying to constrain the parameters of the Chicxulub impactor. Because of its impact in the Yucatan, where there were large beds of organic material, the impact of the Chicxulub event may have been more severe than it would have otherwise been. Current estimates are that climate forcing from the sulfate aerosols are that Chicxulub contributed about 300 W/m2 at the tropopause over about 5 yr. By comparison the 1991 explosion of Pinatubo is estimated to have produced a forcing of about 3 W/m2 over 2 yr. Pinatubo produced an average temperature decrement of about 0.5 K; the Chicxulub impact could have produced a decrement of 10 K. Finally, she noted that even in impacts like Chicxulub, it appears that organic material in the impactor might be able to survive.
Harrison described the Hadean, the first 500 Myr of the Earth from which no rocks remain. However, there are zircons that appear to have survived. Diffusion rates through zircons are low or are claimed to be, and zircons bind tightly to U but not Pb. This makes them ideal for preserving conditions over long times. He has found zircons that are 4.3--4.4 Gyr old. He argues that the 18O enhancement in these is consistent with exposure to water. He then argues that it requires oceans at very early ages. He then described how measurements of Ar and Xe can be used to date the oceans and atmosphere (but I didn't understand this part). He also suggests that there may be some remnant magnetism in these zircons which may allow dating of terrestrial magnetic field. He described this last part as a bit of a long shot, and it sounds as if much of the work is proposed.
Koeberl showed many images of terrestrial craters. There are 160--170 craters with the largest known being 300 km in diameter. He noted the difficulty of assessing whether a structure is a crater is difficult on Earth given the presence of erosional processes. He argues that the presence of shocked material is a requirement for making a definitive determination. He also argued that there is no evidence that the Permian-Triassic massive extinction was due to an impact.
Karen Meech noted that comets may be heated after their formation as
they fall into the presolar disk condensed to the midplane. She noted
that ices condense at temperatures T < 1000 K, thereby trapping
gasses. (I think the point is that by sampling comets one might
obtain samples of presolar gasses.) She also noted that current
models suggest that the Oort comets were formed in the Jupiter-Neptune
region of the solar system and then ejected while KBOs were in their
current location. The result is that Oort cloud comets might be more
processed than KBOs. She also noted that radio observations show that
chemistry may be taking place in comet comae. Finally, she noted that
many comets/KBOs show complex spectra, indicating some amount of
processing; this includes objects for which there appear to be
hemispherical differences or changes on surface over time.
Paul Davies discussed "biological determinism," the notion that the
physical laws are "rigged" in favor of life. He argues that cells are
quantum computers because genetic databases, i.e., DNA, must be
"random" yet specific in order to contain sufficient information
content. Regular objects have a low information content. Because
Darwinism allows for both randomness yet specificity, it allows for a
high information content. Others have suggested molecular Darwinism,
in which the precursors of biological molecules would have been
"selected." Moreover, molecules employing quantum computer aspects
could have searched the large parameter space from the first
self-replicating molecule to the RNA world. He also engaged in a bit
of numerology, noting that Grover's algorithm is a way for a quantum
computer to query an unsorted database of N items Q times. For Q = 1,
N = 4. He argues that this corresponds to the 4 bases of DNA. He
also tried to argue that living systems could maintain coherence in a
noisy environment, providing quiet oases in which the computing could
occur. He suggested the way that an enzyme wraps itself around RNA(?)
during the protein synthesis process would be such an example of
isolation from the environment in order to maintain coherence.
Blair Hedges described the tree of life. He noted that it may be impossible to construct a unique tree given that eukaryotes may have experienced considerable lateral transfer from other kingdoms. The molecular clock indicates the time of the genetic split so molecular dates will or should proceed fossil dates. He wants the plant-animal split to have occurred 1.5 Gyr ago, which means that animals were present 1.5 Gyr ago. He noted that mitrochrondin originated 1.5 Gyr ago. He also noted a relatively rapid increase in the rise of complexity in several lineages. Thus, he is also comfortable with the Cambrian explosion. (In conversations with another biologist later in the meeting, I learned that other biologists are less confident, possibly much less so, of his conclusions than he is.)
Karen Junge is studying whether bacteria can survive in ice. She has developed an in situ microscope for studying bacteria in Artic sea and lake ice. Her ice cores are 1--2 m thick within which there are small cracks within which brine water forms brine pockets. Bacteria attach to the walls of the brine pockets, which she indicated were essential for the bacteria to survive and metabolize. She showed evidence of bacteria metabolism and motility activity even at -20 C.
Manuel described the RNA world, in which RNA would have worked both as the information coding molecule and a protein for metabolism. DNA appears to be modified RNA suggesting that RNA came first. RNA may have problems in thermophilic conditions, but salts may stabilize RNA against temperature.
Janet Siefert described ribozyme, a piece of RNA that encodes information but also acts like an enzyme to construct proteins. She described a series of laboratory experiments in which various selection criteria and mutations were applied to a collection of RNA. Via the laboratory protocols, she could obtain a "family history" of the final products (after something like 60 "generations"). She finds a general trend of decreasing diversity after selection and that it is difficult to explore new regions after the molecule becomes more specialized.
van Kranendenk presented an exhaustive analysis of a region of 3.49 Gyr old rock. He claims to find stromalites and that the geology of the rocks indicate that they were on the edge of a hydrothermal vent, probably on a seafloor. Although later he appears to indicate that another possibility is that the geology might indicate a region around a volcano, possibly after it became dormant but hot water continued to seep up. The caldera of the volcano would have then become submerged by an ocean or become a volcanic lake. He also suggests that material may have been recirculated, possibly including entraining bacteria and entombing them below ground. I believe he suggests that some biogenic material has been found in the rocks but that it was found in a location that suggests it was underground at the time the rocks solidified.
Lori Marino attacked the question of what is the parameter fi in the Drake equation. She used numerical ability, self-awareness, and technology to "define" intelligence although never really said that's how she was going to define intelligence. She pointed out that none of these characteristics are unique to humans. Many species have rudimentary numerical ability and share characteristics with humans. For instance, humans are slower to distinguish that nine objects is larger than eight than they are to distinguish that nine objects is larger than two, just like many other species. Her research suggests that dolphins appear to exhibit self-awareness. (She also spent far too much time in her talk arguing for "objective" approaches to science.) She also commented on chimpanzee culture including the possibility of doing chimpanzee archeology. Other species also appear to exhibit cultural differences including sperm whales, humpback whales, some monkeys, and dolphins.
Varki reiterated the Primatae tree; orangtuns split about 13 Myr ago, then G. gorilla about 8 Myr, P. troglodyte and P. pygmus(?, bonobos) about 5 Myr ago. He claims that H. sapiens differ structurally from other primates significantly. He described cell membranes; they are lipids with sugars sticking up from the membrane. At the ends of the sugars can be various compounds, but he focussed on a particular one: sailic acid. H. sapiens' membranes contain only the Neu5Ac form of sailic acid; all other great apes have a roughly 50%/50% mix of the Neu5Ac and Neu5Gc forms. Moreover, even in mammals having large quantities of Neu5Gc, it is never found in the brain. He wondered if somehow Neu5Gc is not a compound one wants in a mammalian brain. (He also noted that by eating animals one will ingest only trace amounts of Neu5Gc, with the exception of red meat like lamb and beef, which are high in Neu5Gc.) He claims that H. neandertal have the same Neu5Ac sailic acid form as does H. sapiens, indicating that the H. sapiens/great ape difference in sailic acid is older than the H. neandertal-H. sapien split. (It's not clear to me whether the sailic acid difference is a cause or effect.) He also noted, though said he was not pursuing, that there are differences in the thyroid produced between H. sapiens and P. troglodyte. The thyroid production influences when the skull sutures close. Too much and the sutures close too early (or too late?); too little and the sutures close too late (too early?). The larger human brain would have required a change in the thyroid production from our great ape ancestor. In the discussion session (or later?), there was some questioning of whether his estimates of the structural differences between H. sapiens and the great apes was meaningful. (After the conference, I was talking with Ron Ekers who indicated that he had attended another conferenced at which somebody reported finding that human susceptibility to UV radiation, e.g., skin cancer, may be caused by a gene mutation that also produced our circadian clock. The same gene seems to control both the circadian clock and the UV damage repair capabilities; other close species have a much higher capability to repair UV damage in their cells but a decreased circadian clock. Neither of us is clear what the impact of this is, though.)
Blair noted that recent molecular studies have tended to reorganize the animal kingdom so that there are two major branches with no intermediate forms. She is a student of Blair Hedges and repeated the quite early dating for animals. In the discussion session, Malcom Webster noted that stromatalites show a pronounced decrease about 1 Gyr ago, which he has suggested in the past might be an indication of increased grazing by early animals, though no other evidence of such animals has been found.
Simon Conway-Morris wants DNA to be the optimal coding mechanism. He is also a strong proponent of convergent evolution between worlds. His argument is based on the large parameter space for life to explore (at one point he cited the number 1055 as the number of possibilities of something, though I'm not sure I understood what the "something" is) as compared to the relatively limited region of parameter space that it has explored. His inference is that life is fairly constrained so life on other worlds would look much like (though not identical to) life on this world.
McShea asked the question of whether intelligence is driven to increase or occurs more by a passive, diffusion-like process. He is focussing on Mammalia. As a measure of "intelligence," he uses encephalization. Thus far, he has studied only odontocetes (toothed whales, a "group" that includes dolphins). He uses three measures of whether encephalization increases in time, whether the minimum has increased, an ancestor-descendant test (is the ancestor of a particular species more or less likely to be less encephalized), and skewness. His initial results suggest that there has been no increase in the encephalization of odontocetes over time. However, I am somewhat skeptical of his encephalization measure. The encephalization of a species is determined by comparing its measured brain size to that expected, where the expected size is derived from a linear regression of a large sample of brain and body masses. The problem is that there is a fair amount of scatter in the brain and body masses and so the linear regression should imply some uncertainty in the expected brain size. He did not seem to be taking this uncertainty into account.
McCowan/Doyle described information theoretical analyses of vocalizations of various mammals. He showed that all human languages have similar densities of information. Brenda McCowan has attempted to identify dolphin vocalizations (squeaks and whistles). They find that dolphin vocalizations have similar information densities (or perhaps slightly less but still far from random) as to human speech. Moreover, human infants babble, and he showed how the information density of human infant babble actually decreases during the first few years then begins to increase as the child moves through adolescence and into adulthood. Dolphin babies also babble, with their initial vocalizations being quite unstructured but becoming more structured (with higher information densities) as they age. (Interestingly, dolphin babies do not show the decrease in information density during their first few years as do human babies!) They have also been able to construct a dolphin syntax diagram; thus, given a particular kind of squeak or whistle, they can predict the odds that another kind of squeak or whistle will follow (much like given a 't' in an English word, we know that there are fairly high odds that it will be followed by an 'h').
Michael Rampino described super volcano eruptions. During the twentieth century various volcano eruptions resulted in average surface temperature decreases of about 0.5 C in the few years following the eruption (e.g., Mt. St. Helens or Pinatubo). In the case of Mt. St. Helens, it produced about 1 km3 of ejecta. He then showed a number of super-eruptions, many from the western US, in which of order 1000 km3 of ejecta were produced. He focussed in on Toba, a volcano in Indonesia, which erupted about 73 kyr ago. It was the equivalent of about 100 Pinatubos and probably produced a global cooling of 5 C. Interestingly, he claimed that there is genetic evidence suggesting a population bottleneck in both humans and chimps about 60--70 kyr ago. (I think by "population bottleneck" he means that the number of individuals dropped to a rather low number; for humans, I think he cited figures of 3000--10,000.) Toba-magnitude eruptions occur on average about once every 50 kyr, about twice the frequency of impacts of 1 km objects. (I also noted that vulcanologists tend to hold their conferences on the slopes of [one hopes!] extinct volcanoes. He had just come from a conference in Santorini and was planning for one near Toba.)
Blumberg's talk was entitled "Primitive Life," but a more accurate title might have been "Everything You Didn't Want to Know about the Hepatitis B Virus."
Lazcano distinguished between "ancient" and "primitive." He claimed that even hyperthermiphilic organisms today still use "modern" methods of metabolism, suggesting that they may be primitive but not ancient. (I wonder if lateral gene transfer may account for some of this?) He described two possibilities for early life, either "abiotic synthesis and heterotrophism" or "CO2 fixation and autotropic." Pyrite can fix CO2, allowing organic chemistry to proceed. This would be an example of the latter of the two processes, and it might produce organisms with no cell membranes. He also noted that it is easy to get organic monomers, but difficult and not clear how to get polymers. He asked the question of whether there was prebiotic synthesis of RNA in order to get to the RNA world. He also described the Fisher-Tropse reaction as CO + H2O + NH4 chemistry occurring an Fe, Ni, or clay surface and producing amino acids.
Kent Cullers described an all-sky survey and remarked that 1 Petaflop is not enough computing power to do such a survey. He genuflected to Moore's Law, though. He also noted that it might be possible to detect transient pulses, and even showed a couple of examples. I asked him about plans to archive transient pulses to do things like searching for clustering on the sky. He said that archiving would be done for short periods (~ 1 hr) but not long periods because nobody would believe such an archive. (As interesting as the subject matter of his talk was the way he presented it. He motivated various aspects of SETI by using radio signals from shortwave broadcasts and the like that he had taped. Thus the first part of his talk consisted of replaying these taped signals. Because Cullers is blind, his talk was based far more on auditory rather than visual examples.)
Andrew Howard described a search for nanosecond optical pulses. He showed that with current technology it would possible to outshine a star on nanosecond time scales by a factor of 1000 or so. His estimate was that one could collect 350 photons from his model transmitter (a Helios laser with 1015 W[?] directed into a Keck telescope). In comparison with such a transmitter, the typical solar type star contributes only of order 10,000 photons in 1 s so most of their bins are empty. (I cannot remember the bin width, something between 1 and 100 ns.) The search has conducted of order 14000 observations in 1821 hr. They use multiple detectors in order to discriminate between detector glitches and actual signals. They have had a few "hits," but Monte Carlo simulations suggests that all of these are consistent with a background rate. One of the best quotes of the conference: "Stars are dark on nanosecond time scales."
John Campbell is an archaeologist, and he sketched human technological and cultural development. For instance, fire was captured between 0.3 and 1 Myr ago, elaborate tools were being made in Africa by 80 kyr, but then took of order 40 kyr to spread around the world, people had voyaged to Australia by 50 kyr ago (he claimed that this required long sea voyages, but I wondered later if lower sea levels during an Ice Age might have made it much easier), humans spread to the New World between 12 and 30 kyr ago, domestication of animals occurred 10 kyr ago, cities were developing by 5 kyr ago, and the Polynesian navigators were colonizing the Pacific islands by 2 kyr ago. He went on to argue that certain space-faring sites should be preserved, mentioning at least Apollo 11 (0.03 kyr ago :), some of the Martian sites, the Huygens landing site on Titan, and possibly any Jovian sites that might result from various landers; Venusian sites might be interesting but difficult to preserve. There's a difference in motivations in preserving these sites, though, and other archaeological sites. One preserves (or tries to preserve) a Mesopotamian city because we might learn something about its inhabitants; one preserves Plymouth Rock because of its emotional significance, not because we hope to learn something about the Pilgrims from their landing site. I asked him about this motivational difference during the discussion session. I don't think he understood my question, but he agreed that there was a difference in motivations.
Eric Korpela summarized SETI@home. Because of the large amount of computing power available to them, far larger than they had expected, the team is looking at and beginning to incorporate more sophisticated or more complicated detection schemes in the code.
John Dreher summarized the ATA. He pointed out that, with the current Project Phoenix efforts examining 1000 stars, if 10% of those stars have planets (not all of which would necessarily be terrestrial), they might be looking at only 100 planets. That's not much. With the ATA, they expect to look at 1E5 stars, from which statistical analyses about planets with technological civilizations could start being done.
Paul Demarest summarized a search for radio and optical pulses. They are searching for radio pulses with 0.4 microsecond time resolution. The original motivation was to search for pulses from exploding black holes.
Shirai described a search for ETI signals at the 22 GHz emission line of water. (He used the VLA and, as far as Ron Ekers and I could figure out, that was for sensitivity not angular resolution purposes.)
Shelley Wright described an optical SETI program. They use a triple coincidence scheme to try to reduce false alarms, though, they still have 5 false alarms in their first 2000 observations. They are also looking at Fourier transforming the collected time series as other avenue to hunt for pulses.
Many of the talks on July 12 were focussed on the sociological and educational aspects of bioastronomy. By and large I listened to these with half an ear while working on other things. The talks were interesting, but I rationalized not taking any notes by the fact that I am not a teacher currently.
Seth Shostak discussed intelligent design (ID) vs. SETI. ID is the latest attempt by fundamentalists to subvert science education by requiring that their religion be taught. Attempts to force creationism into schools in the US have become far more sophisticated (dare one say that they have evolved in response to the selection pressure applied against them?). One important point he made is that ID proponents argue that their "analysis" is similar to that of SETI: Detection of a complex signal from a star would be taken as evidence of intelligence. He pointed out that one fallacy with this argument is that SETI programs would be quite happy detecting a simple signal (a la Jill Tarter's "cosmic dial tone"). Other talks also picked up on the difficulty of teaching bioastronomy because of the prominent nature of "evolution" within it, not only evolution of living organisms but the Universe is often said to have evolved (i.e., changed) from an initially hot dense state to its current cold rarefied state.
Ron Ekers summarized the conference with a look toward the future. He started with an apt criticism that there were few "big picture" talks to put things in context and the use of jargon may have obscured rather than illuminated subjects. He makes a point that there is a big ratio between our technological age and the age of the Galaxy. He suggests that the chances of just a few other civilizations is negligibly small. There is probably either 1 civilization or billions.
Frank Drake noted a result not presented at the meeting. Known planetary systems are "dynamically saturated"; attempting to insert other planets into the systems renders the systems unstable. He mentioned Troödon (sometimes called Stenonychosaurus inaccurately); of approximately our dimensions, bipedal, with binocular vision (rare for dinosaurs) with a brain mass comparable to that of a H. sapiens infant.