Hitch-Hiker’s Guide to Biology’s Second Datum
Hitch-Hiker’s Guide to Biology’s Second Datum
An international team of scientists this week joined forces onboard the space shuttle Columbia for a 16 day marathon investigating microbial function in space.
Astrobiology Magazine’s editors conducted interviews in the middle of the shuttle mission with two leading scientists about some of the experiments’ broad goals. One objective is to investigate the hypothesis otherwise known as ‘panspermia’ – can life survive interstellar transport?
|Dr. David Warmflash, M.D., is a National Astrobiology Institute Associate, NASA Johnson Space Center’s Astrobiology Institute, Houston, Texas|
|Dr. Neil deGrasse Tyson, Ph.D., is the Planetary Society’s Vice President, the Frederick P. Rose Director of the Hayden Planetarium, New York City and Visiting Research Scientist and Lecturer, Princeton University.|
Astrobiology Magazine (AM): What is your personal opinion on the panspermia hypothesis?
Warmflash: First of all, so far we don’t have any evidence one way or another. I suspect that the conditions for the emergence of life from non-living material occur on many planets and moons and that life originates over and over throughout the Cosmos.
Panspermia probably occurs at least on a limited level spreading life out from its points of origin. One of the interesting things that we will want to investigate if we find native life on Mars is whether or not it and Earth life are actually the "same" life, meaning that they share common ancestry (we will be able to check this using molecular methods). If we find this to be the case, it will not necessarily mean that life somewhere else, even within our own solar system, say on Europa, is related to Martian/Earth life.
If we find life on Mars and Europa then we could find that Earth and Mars share one type of life while Europan life has a separate origin just as easily as we might find that all three share the same origin. Many scenarios are possible (though life arriving from other star systems is more problematic) although the most interesting, I think, would be the finding of life in our own Solar System, whether on Mars or elsewhere that does NOT share ancestry with that of Earth. If life emerged independently twice or more within our own tiny star system then it’s probably all over the Cosmos.
The important concept is that the possibilities of multiple origins of life and panspermia are not mutually exclusive. Both can and probably do occur in nature.
Tyson: Panspermia remains an intriguing idea, perhaps even likely, for the spread of life among neighboring fertile planets. But before we get too excited about the idea, consider that if life is easy to make from non-life (given the right conditions and ingredients) then the panspermia is not a required condition for life, even if true.
And if life is hard to make from non-life then it offers no insight into how life formed in the first place. One frustrating feature of panspermia is, if we find life on another planet, say Mars, and its identity is encoded in DNA, we will have no way to tell whether we are descendants of Martians, whether they are descendants of Earthlings, or whether DNA itself is an inevitable, easy to form pre-requistite for life in the universe.
|The scanning electron micrographs show Saccharomyces cerevisiae (yeast) grown in microgravity (A) and gravity (B). In microgravity yeast cells grow in clusters. S. cerevisiae will be one of the fungal strains tested on STS-107 for changes in growth pattern and physiology.|
AM: What kinds of effects of space on cells and DNA would you expect to see?
Warmflash: The NASA Johnson Space Center Astrobiology Institute is collaborating with Eran Schenker of IAMI on three experiments in the ITA CIBX-2 package. One of these three is the panspermia experiment, sponsored by the Planetary Society. The line in the Planetary Society press release on "seeking data about the effects of space on cells and DNA" actually refers to these three experiments as a whole. In the panspermia experiment (GOBBSS) we will be using scanning electron microscopy (SEM) to visualize a biofilm made of bacterial cells and extracellular organic material that we expect to form on mineral surfaces.
We expect that biofilms will form both in the spaceflight conditions and ground control but that there may be differences in features of the biofilms such as thickness and/or distribution of the film on the mineral particles. SEM will not tell us anything about the DNA of the bacteria. The effects on DNA have to do with one of the other two IAMI/JSC experiments (not involving the students), this one in collaboration with scientists at Hadassah Medical and Dental Schools (Jerusalem), in which we are looking the effects of space flight on the expression of a certain gene called recombinant human Bone Morphogenic Protein (rhBMP-2) in specially engineered mesenchymal stem cells. The results will have implications for the study of osteoporosis in space and on Earth.
AM: So the idea is to release bacteria (what kinds?) onto a meteor-like substrate, and look with scanning electron microscope (SEM) imagery for biofilm formation, correct?
Warmflash: Correct. The material is originally from basalt rock which has been not only sterilized to kill all bacteria but subsequently treated with atomic oxygen plasma (single atoms of oxygen as opposed to molecular oxygen) which destroys all organic material on the surface of the rock which has been ground into small chips (0.5 to 1.0 mm).
What is left is pure inorganic mineral, like what makes up the inorganic component of the Mars meteorites (such as ALH84001).
So we are starting out with material that has no biofilm on it or anything else organic and this material is kept sterile until the shuttle reaches orbit. The experiment begins in orbit when it is exposed to a bacterial culture.
We are using four different species of the genus Bifidobacteria. Bifidobacteria are a type of Gram positive obligate anaerobes that happen to be good for you if you eat them. Since we developed GOBBSS as a last minute experiment (because of a last minute opportunity), we had to choose from what was already the list of approved organisms. Since the Gram positive strains are thought to be among the most ancient of all Earth life (thought to be ancestors of the Gram negatives), we wanted to use a representative of them in the experiment and since Mars, interplanetary space, and even Earth of the past were free of oxygen, anaerobic organisms make sense. In subsequent experiments we might try various other organisms.
But for now the aspect of bacteria growing on meteor-like material and in weightlessness is new and for this step the Bifidobacteria should work fine.
|Biofilms on rock surfaces are rapidly mineralized and can be preserved for billions of years as biomarkers of ancient biology|
AM: Can you suggest any place where we could find perspectives on the experimental goals or panspermia?
Warmflash: This isn’t something that can easily be investigated experimentally.
In GOBBSS we are seeing how well bacterial adapt themselves to biofilm formation on a meteorite in weightlessness. The biofilm would be protective and finding that there are no major problems in forming them would support the idea that panspermia via meteorite is possible. But, as in the case of the studies showing that meteorites can easily travel from the surface of Mars to the surface of Earth without getting too hot in their interior, it will not prove that pansperimia happened in the case of Earth.
The way to do that would be bring back living samples from Mars and find that they are distant relatives of Earth life, more distant than the relation between the most distantly related Earth taxa but still using DNA and operating according to the same or very similar genetic code (the genetic code is the language while DNA is the alphabet) as those of Earth.
In addition to Dr. Eran Schenker of the Israeli Aerospace Medical Institute, other scientists advising on the experiment include Palestinians Johnny Younis of Poria University Hospital, Nazareth, Dr. Ahmad Tibi, physician and Arab member of the Israeli Knesset; and Dr. David McKay of NASA Johnson Space Center. Dr. David Warmflash helped the students design the experiment and was responsible for bringing it to The Planetary Society as a peaceful science initiative.
Seeds of Peace Project by Planetary Society
"Space exploration is a symbol of the linked destiny we all share as humans and as residents of the home we call Earth," said Dr. Neil deGrasse Tyson, Vice President of The Planetary Society. "This project exactly fits the mission of The Planetary Society — to inspire the people of Earth to explore new worlds and seek other life through research, education and public participation."
The two university students, an Israeli and a Palestinian, are participating with Dr. Eran Schenker of the Israeli Aerospace Medical Institute in seeking data about the effects of space on cells and DNA. Such data might provide new insight to theories of life traveling between planets. Schenker is conducting a series of cell biology experiments that will fly on the Columbia space shuttle as part of ITA’s Commercial Payload, the CIBX-2. This is an ITA corporate biomedical payload performing both cancer research and student experiments through a commercial Space Act Agreement between ITA and NASA.
Tariq Adwan, a Palestinian biology student from Bethlehem, and Yuval Landau, an Israeli medical student from Tel Aviv, will be co-investigators on the student experiment. Adwan is currently attending College Misericordia in the United States, while Landau attends Tel Aviv University in Israel.
In addition to Schenker, other scientists advising on the experiment include Palestinians Johnny Younis of Poria University Hospital, Nazareth, and Dr. Ahmad Tibi, physician and Arab member of the Israeli Knesset; and Dr. David Warmflash and Dr. David McKay of NASA Johnson Space Center. Warmflash helped the students design the experiment and was responsible for bringing it to The Planetary Society as a peaceful science initiative.
"The experiment is primarily a demonstration to show how people, united by a common goal, can work together to answer questions that have intrigued all humanity for ages," said Warmflash. "However, this is also a useful and original experiment that may contribute valuable insight into the question of life in the cosmos."
The GOBBSS experiment will help test the much debated "panspermia" hypothesis the belief that microorganisms from other planets arrived on Earth in the distant past and helped spur the development of life on Earth.
"Especially in this unstable time," said Younis, "I am happy to take part in the selection process of students from both sides to work together on a united bio-space study."
The experiment, which combines ideas proposed by the two students, involves a sample of bacterial cells enclosed within a compartment in a special container carried in the shuttle’s Spacehab module. Once the shuttle is in orbit, an astronaut will activate the experiment container, releasing the bacterial sample into a second compartment, which contains inorganic crystal material similar in structure to the meteorites that have traveled from Mars to Earth. Before returning to Earth, the astronauts will deactivate the study, causing a fixing agent from a third compartment to mix with the bacteria-exposed material.
Once the container has been returned to Earth, the students and their advisors will examine the bacteria using scanning electron microscopy (SEM) to see how well the bacteria grew on the material, if at all. They will compare the results with those from a parallel experiment done on the ground.
"If the organisms produce a biofilm under weightless conditions, it will add weight to the hypothesis that organisms can be transported by meteorites from one planet to another and possibly seed a lifeless planet," said Warmflash.
Seeds of Peace, an organization dedicated to increasing understanding and cooperation between Israeli and Palestinian youth, is working with The Planetary Society in this project. Seeds of Peace and the Israeli Aerospace Medical Institute advertised the experiment to university students in Israel and Palestine to seek their participation. The Peres Center For Peace is also helping support and promote the Science for Peace project.
"The Planetary Society believes that the study and exploration of space not only expands our horizons out into the universe, but also brings together the people of Earth," said Dr. Louis Friedman, Executive Director of The Planetary Society. "The organization has long been committed to advancing international cooperation in peaceful space exploration, beginning with cooperative ventures with scientists in the Soviet Union in the 1980′s and continuing today with programs around the world with — and in — many nations. The GOBBSS experiment is especially apropos since the concept of panspermia reminds us that life everywhere is connected and that what we share far outstrips what divides us."
Related Web Pages
Space Shuttle (STS-107 Mission) Scientific Factsheets
Planetary Society Experimental Description
Microbiology in Microgravity (PDF)
The Search for Life in the Universe (N. Tyson, testimony to Congress)
Natural Transfer of Viable Microbes in Space 1. From Mars to Earth and Earth to Mars, Mileikowsky, et. al,.Icarus 145, 391-427 (2000).
Ancient Mars Life Studies (Spaceflight NASA)