Updated with MP3 audio in Interview.
“That’s one of the biggest questions for NASA as they go out to search
for signs of life elsewhere. What would alien life look like?”
– Michael Callahan, Ph.D., Astrochemist, NASA Goddard
Reposted December 9, 2024 – August 26, 2011 Greenbelt, Maryland – There is an Astrochemistry Lab at the NASA Goddard Space Flight Center in Greenbelt, Maryland. There, Research Physical Astrochemist Michael P. Callahan, Ph.D., has been studying a dozen carbonaceous chondrite meteorites that have fallen from space to Earth. Nine of them came from Antarctica because he wanted to concentrate his research on meteorites that would be more protected from terrestrial contamination. The cold, icy environment of the South Polar region provides better preservation. What Dr. Callahan has been looking for in the carbon-rich meteorites are chemistries related to life that had to have been created in space.
Scientists have been discovering some components of DNA in meteorites since the 1960s, but researchers were unsure whether what they found had actually been created in outer space – or was only terrestrial contamination from Earth’s environment where meteorites have landed.
So far, Dr. Callahan has found adenine and guanine, which are nucleobase components of the DNA molecule in all life on Earth. They are part of the code that tells the cellular machinery which proteins to make. And for the first time trace amounts of three molecules related to nucleobases almost never found in biology have been confirmed and most likely were produced in a completely non-biological chemical reaction within the meteorite.
Dr. Callahan is confident that the nucleobases and nucleobase analogs he has found were created in the meteorites as they originally traveled in outer space. His work was published in the August 2011 Proceedings of the National Academy of Sciences.
Michael P. Callahan, Ph.D., Research Physical Astrochemist, Astrochemistry Lab, NASA Goddard Space Flight Center, Greenbelt, Maryland: “We find building blocks of DNA in meteorites. Most people have seen a picture of DNA, the double helix structure. So if you look at it, it looks like a twisted ladder. These are very, very large, complex molecules that are essential for all of life on Earth and they carry the genetic information.
So, if you break down the structure of DNA a little bit further, they are made up of repeating components called nucleotides. You can take that nucleotide building block and break it down into three pieces:
1) a nucleobase
2) a ribose sugar molecule
3) a phosphate group
What we find in meteorites are the nucleobase. The easiest way to picture this is if you imagine the double helix structure, the twisted ladder, the DNA. We’re looking at the rungs of the ladder.
And so our discovery is that when we look at meteorites and we find these nucleobases and nucleobase analogs, it looks like the product of a chemical reaction. So these things can be created in space on the meteorite.
ISN’T THE IMPLICATION THAT IF NUCLEOBASES COULD BE CREATED IN SPACE ON CARBONACEOUS CHONDRITES AND THEY SLAM INTO THE EARTH, THAT THOSE NUCLEOBASES MIGHT HAVE THE ABILITY TO START LIFE ON A PLANET?
That’s right. And that’s basically one of the most interesting implications for us in that during an early Earth when these meteorites were coming in constantly, they might have brought in some significant starting materials that could have assisted the origin of life on Earth.
And then another standpoint is that if you have these meteorites being distributed everywhere else in the solar system or potentially outside the solar system, maybe it could have assisted the development of life elsewhere as well.
I READ AN ICARUS PAPER THAT DR. FRANCIS CRICK, WHO RECEIVED THE NOBEL PRIZE IN 1962 FOR THE DISCOVERY OF THE DOUBLE HELIX STRUCTURE OF THE DNA. A DECADE LATER IN 1973, DR. CRICK TEAMED UP WITH CHEMIST DR. LESLIE ORGEL AND THEY PROPOSED A PAPER CALLED ‘DIRECTED PANSPERMIA.’ THOSE TWO SCIENTISTS WERE PROPOSING THAT BECAUSE WE HAVE ONLY ONE DNA MOLECULE ON THIS WHOLE PLANET, THAT DID NOT MAKE SENSE TO THEM. SO THEY WERE PROPOSING THAT LIFE ON EARTH WOULD HAVE STARTED FROM SEEDING FROM OUTER SPACE IN WHICH THE DNA MOLECULE UPON ARRIVING IN WHATEVER IT ARRIVED IN WOULD HAVE CLONED ITSELF TO MAKE NOTHING BUT THE DNA MOLECULE THAT WE FIND IN LIFE ON EARTH.
Sure! I can see that as one theory, or even something earlier – an alternative structure to RNA that used nucleobase components, but not necessarily maintained the structure of RNA or DNA. That’s a possibility.
But since we don’t really know the conditions of the early Earth that well, a lot of that record has been erased. We don’t really know what the chemistry was on the early Earth at the very beginning. We don’t know what was being pumped out; what types of building blocks were being made.
WOULD YOU AGREE THAT DR. FRANCIS CRICK AND CHEMIST LESLIE ORGEL IN THAT ICARUS PAPER IN 1973 COULD BE CORRECT AT LEAST HYPOTHETICALLY THAT AN ENTIRE DOUBLE HELIX DNA MOLECULE MIGHT HAVE COME INTO EARTH ON SOMETHING LIKE A CARBONACEOUS CHONDRITE, LANDED ON EARTH AND CLONED ITSELF AND THAT IS WHY ALL EARTH LIFE WOULD BE DOUBLE HELIX DNA?
I haven’t read that paper in a long time. I don’t want to comment too much on it. My background in chemistry deals with small molecules, but a lot of times DNA does not survive that long. So to have those molecules completely intact without breaking down, I think would be a surprise.
YOU PROBABLY REMEMBER – I THINK IT WAS IN A NEWS MAGAZINE – THAT FRED HOYLE, THE ASTRONOMER, WAS QUOTED AS SAYING THAT THE IDEA THAT THE DOUBLE HELIX DNA MOLECULE COULD HAVE RISEN FROM SOME KIND OF PRIMIEVAL STEW IN THE OCEANS AND BECOME THE MOLECULE THAT IT IS WOULD BE LIKE A TORNADO COMING DOWN INTO A JUNK YARD AND COMING OUT WITH A 747 AIRLINER.
THAT HAS ALWAYS STRUCK ME AS BEING THE CHALLENGE: WHERE DID LIFE ORIGINATE FROM ON THIS PLANET?
Yes. And I think it is because we really are at the tip of the iceberg for understanding these things.
AS A HUMAN LIVING ON THIS PLANET, ARE YOU PERSONALLY ASTONISHED THAT THE DOUBLE HELIX DNA MOLECULE IS THE ONLY MOLECULE FOUND IN LIFE ON THIS PLANET?
As we know it, absolutely! It’s fascinating. And it goes back to what we look at – these DNA molecules really use only four structures. Then if you throw in RNA, it’s five nucleobases. And now we are learning there might be a sixth nucleobase. But it is amazing! It’s amazing that with things being so diverse, why is this (DNA) so specific? It’s a big mystery. Because it started out that way? Evolved that way? But from a research standpoint, it gives us something to target very specifically. That’s kind of how this study evolved.
We looked at these compounds because they were so important, because they were so specific and yet so universal to life.
Why Does All Earth Life Have the Same DNA?
BACK IN 1973 IN THEIR ICARUS PAPER, DR. CRICK AND DR. ORGEL EVEN RAISED THE POSSIBLITY THAT THERE ARE ADVANCED INTELLIGENCES BEYOND THIS SOLAR SYSTEM INTENT TO SEED LIFE ON PLANETS AND THAT THE DOUBLE HELIX DNA MOLECULE MIGHT HAVE BEEN SPECIFICALLY PLANTED BY ADVANCED INTELLIGENCES.
I can’t disprove what they are saying, obviously. But to me when we do our measurements and we are looking at these nucleobases, our explanation about why these are indigenous to the meteorite is that it does resemble a simple chemical reaction – a chemical reaction involving hydrogen cyanide, ammonia and water. That is what is likely to be making these nucleobase and nucleobase analog structures.
IF THAT IS TRUE, DOESN’T THAT MEAN THEN THAT THE NUCLEOBASES COULD BE ON CARBONACEOUS CHONDRITES THROUGHOUT THIS UNIVERSE?
Absolutely! That’s the great thing – these molecules could be in all sorts of carbonaceous chondrite meteorites and they are being dispersed everywhere. But that’s a far different cry from saying the full DNA sequences are in the meteorite.
I’ve gotten this question before when it’s like, ‘Well, how do you know that this is still chemistry and not the remnants of some sort of strange alien DNA?’
What Does Alien, Non-Human, DNA Look Like?
The answer is that since we don’t know what alien DNA looks like, is this the remnants of that? Or is this the chemical reaction? For us, we can’t draw comparisons to something we don’t have a measurement for or a standard against. But the nucleobase and nucleobase analogs we can explain in terms of a simple chemical reaction, at least for now.
HERE WE ARE – HUMANS ON A PLANET THAT HAS BIODIVERSITY OF LIFE ALL HAVING A DOUBLE HELIX DNA MOLECULE. IF THIS DOUBLE HELIX DNA WAS SEEDED HERE IN DIRECTED PANSPERMIA, AS DR. CRICK AND DR. ORGEL HYPOTHESIZED IN THEIR ICARUS ARTICLE, WE WOULD NOT HAVE ANY WAY TO PROVE THAT WE WERE THE PRODUCT OF AN EXTRATERRESTRIAL MANIPULATION OF DNA HERE.
That’s very true. That’s one of the biggest questions for NASA as they go out to search for signs of life elsewhere. What would alien life look like? People have the idea that if it looks similar to us, how can you distinguish that? It is a big question and a major research question as well and people endlessly debate it.
Mars Science Laboratory
Scheduled to launch Thanksgiving 2011 for Spring 2012 arrival.
NOW, THE MARS SCIENCE LAB IS GOING TO HOPEFULLY LAUNCH NEXT YEAR. IT IS SPECIFICALLY DESIGNED TO LOOK FOR ORGANIC LIFE ON MARS. DO YOU THINK IT COULD BEAT THE RACE IN FINALLY FINDING SOMETHING IN THE CATEGORY OF ORGANIC LIFE?
I sure hope so! I have friends on that project and it would be great to see success. It (MSL) is the most state-of-the-art instrumentation for that type of analysis. So I think if anything has a good shot at detecting organic molecules, it would be this. NASA is putting forth a great effort to see if they can answer that question on Mars.
IF THAT LANDER DOES FIND ORGANIC LIFE AND IT TURNED OUT TO HAVE A DOUBLE HELIX DNA LIKE EARTH, WHAT WOULD YOU CONCLUDE?
I’m not sure it can go that far. I mean, it will basically measure organic molecules, so I don’t believe anything is specific for DNA analysis. It would be basically the things that I would be looking at, which would be small molecules like amino acids and nucleobases. I don’t think there is anything there that can actually measure a large macro molecule like that, so that analysis I think is going to have to wait.
WHAT WOULD IT TAKE TO GET A SAMPLE BACK FROM MARS TO YOUR LAB OR SOMEONE’S LAB TO SEE IF IT HAS A DNA MOLECULE LIKE EARTH OR IS DIFFERENT?
That’s hopefully a planned mission in the future that would be Mars Sample Return. That would be very exciting to have material from Mars in the laboratory that was collected directly from Mars.
GOING BEYOND WHAT YOU HAVE FOUND SO FAR, DO YOU THINK THE ODDS HAVE INCREASED THAT THERE MUST BE LIFE OUT THERE IN THE UNIVERSE?
I think the likelihood of life elsewhere – the chances have gone up slightly. It takes a lot to go from building blocks to large molecules to a concert of all these different molecules and chemical reactions – to life. But it is a step towards that direction.”
Asteroid Sample Return-to-Earth Mission Planned: 2016 – 2023 Osiris-Rex
NASA has selected the University of Arizona to lead a sample-return mission to an asteroid for the first time in Earth’s space history to return “a pristine sample of a carbonaceous asteroid.”
The mission is named OSIRIS-REx, which is an acronym for “Origins Spectral Interpretation Resource Identification Security-Regolith Explorer.” The mission is scheduled to launch on a 3.5-billion-mile roundtrip in 2016 to a primitive carbonaceous organic-rich asteroid called RQ36 that crosses the Earth’s orbit every September. While orbiting the asteroid, the spacecraft will execute a series of touch-and-go maneuvers at selected sample sites and return to Earth by 2023.
Earth’s Oldest Life Fossils Were In “Oxygen-Free World”
“Such bacteria are still common today. Sulphur bacteria
are found in smelly ditches, soil, hot springs, hydrothermal vents –
anywhere there’s little free oxygen and the sulphur bacteria
can live off organic matter.”
– Martin Brasier, Ph.D., Oxford University, U. K.
A billion years after our solar system formed, there was very little oxygen on Earth. There were no plants or algae to photosynthesize and produce oxygen. The 3.4 billion-year-old cell and bacteria fossils discovered by Dr. David Wacey, Univ. of Western Australia, and Prof. Martin Brasier, Oxford University, imply that early Earth life was sulphur-based, living off and metabolizing compounds containing sulphur rather than oxygen. The scientists guess that beginning life elsewhere in our solar system and the cosmos would be similar.
The Murchison CM carbonaceous chondrite is rich in carbon and more than 100 amino acids have been identified in the various chunks of the broken up meteorite. It was found near the town of Murchison, Victoria, in Australia, on September 28, 1969, at about 10:58 AM after people saw a bright fireball in the sky that seemed to break into three fragments in a cloud of smoke. About 30 seconds later, people felt and heard a tremor. One large chunk weighing 680 grams broke through a roof and fell into hay.
Wikipedia: “Measured purine and pyrimidine compounds are indigenous components of the Murchison meteorite. Carbon isotope ratios for uracil and xanthine of 44.5% and +37.7% respectively indicate a non-terrestrial origin for these compounds. These results demonstrate that many organic compounds that are components of life on Earth were already present in the early solar system and might have played a key role in life’s origin on this planet.”
For further reports about looking for life in our solar system and beyond, please see reports in the Earthfiles Archive:
- 08/26/2010 —Where Did Our Moon Come From?
- 04/30/2010 —M82 Galaxy’s Mysterious Radio Waves
- 01/14/2010 —Death Stars: Supernovae and Gamma-Ray Bursts
- 11/02/2009 —Updated: Is There Life in Europa’s Huge Ocean?
- 01/29/2009 —Part 1: Nanodiamonds Link Outer Space Impactors to Earth Extinctions 12,900 Years Ago
- 01/29/2009 —Part 2: Nanodiamonds Link Outer Space Impactors to Earth Extinctions 12,900 Years Ago
- 08/05/2008 —Perchlorate Discovery by Phoenix Lander Does Not End Search for Life On Mars
- 03/30/2008 —Enceladus Water Geyers Full of Organic Chemicals
- 03/28/2008 —Carancas, Peru, Meteorite in September 2007 – “Unprecedented?”
- 01/12/2008 —Our Milky Way Galaxy On Collision Course with Huge Gas Cloud – 40 Million Years from Now
- 11/01/2007 — Gas Eruptions from Comet Holmes?
- 10/25/2007 —Red Rain Cells of Kerala, India: Physicist Says Still No DNA, But Replication At 300 Degrees Celsius ( 572 F.)
- 10/18/2007 — A Quantum Math Description of Parallel Universes
- 10/11/2007 —Carancas, Peru Meteorite Could Be 10 Tons
- 09/26/2007 —Meteorite Fell in Carancas, Peru – Not Satellite
- 08/03/2007 —The Milky Way Is Devouring the Alien Sagittarius Dwarf Galaxy
- 05/08/2007 —Exploded Star 5 Times Brighter Than Any Supernova Seen Before
- 12/15/2006 —Stardust Comet Mission Reports New Kind of Organics
- 12/01/2006 —Deep Impact and Stardust: Are Comets Made of the Same Stuff?
- 08/19/2006 —Red Rain Cells of Kerala, India – Still No Definite DNA
- 09/16/2005 —”Planet X” and the Kuiper Belt’s Oddballs, “Santa” and “Easterbunny”
- 08/12/2005 —Deep Impact Spectra: Carbonate, PAHs and Some Amino Precursors in Comet Tempel I
- 07/10/2005 —First Data from Deep Impact Crash Into Comet Tempel I
- 06/29/2005 —July 3-4, 2005: NASA “Deep Impact” Spacecraft to Blast Hole in Comet Temple I
- 05/06/2005 —What Are The Straight Lines on Saturn’s Titan Moon?
- 04/20/2005 —Outer Space Impact At Serpent Mound, Ohio, 256 Million Years Ago
- 04/01/2005 —What’s Killing Off Marine Life Every 62 Million Years?
- 02/17/2005 —Iapetus and Enceladus: Baffling Moons of Saturn
- 01/13/2005 —NASA “Deep Space” Craft Will Hit Comet On July 4, 2005
- 12/17/2004 —Is Our Solar System’s Red, Mysterious Sedna An Alien Planetoid?
- 11/17/2004 —European Space Agency’s SMART-1 Satellite Begins Moon Orbit
- 09/20/2004 —Part 1: Martian Water Vapor and Methane Overlap in Equatorial Regions
- 06/25/2004 —Wild 2, An Amazing Comet
- 03/31/2004 —Methane on Mars – Biology? Volcanic?
- 03/15/2004 —Most Distant “Icy Planetoid” in Our Solar System Has A Most Baffling Orbit
- 10/11/2003 —Is Our Universe Finite and Shaped Like A Dodecahedron?
- 09/02/2003 —Updated – Astronomers Don’t Think Asteroid Will Hit Earth in 2014
- 03/07/2003 —Scientist’s Record Sun’s Plasma Interaction with Comet NEAT
- 10/07/2002 —Large Kuiper Belt Planetoid Found Beyond Pluto
- 08/16/2002 —Did CONTOUR Probe Break Apart Or Disappear Into Space?
- 07/25/2002 —Mile and A Half Diameter Asteroid 2002 NT7 Might Impact Earth in 2019
- 07/11/2002 —Hubble Telescope Photographs Seven Objects Traveling In Pairs Beyond Pluto
- 06/01/2002 —Scientists Surprised by Abundance of Water On Mars
- 02/24/2002 —Mysterious Slowing of Pioneer Spacecraft 7 Billion Miles from Earth
- 01/26/2002 —Something Is Perturbing Comet Orbits in the Oort Cloud Surrounding Our Solar System
- 12/01/2001 —1200 B. C. – What Caused Earthquake Storms, Global Drought and End of Bronze Age?
- 11/19/2001 —Update on Underwater Megalithic Structures near Western Cuba
- 11/10/2001 —The Orion Constellation and the Pyramids of Giza
- 11/01/2001 —Astronomy News
- 01/14/2001 —An Australian Zircon Crystal is 4.4 Billion Years Old
- 01/07/2001 —Dinosaur-Killing Asteroid Punched 22 Miles Through Earth’s Entire Crust
- 12/24/2000 —Martian Bacteria?
- 12/03/2000 —Bacteria from Outer Space?
- 10/01/2000 —A Search for Earth’s First Life
- 03/11/2000 —Is 433 Eros Asteroid Younger Than Expected?
- 02/16/2000 —433 Eros, Orbiting An Asteroid Up Close
- 10/25/1999 —A Mysterious “Perturber” at the Edges of Our Solar System
- 06/15/1999 —Current Brightest Binocular Comet and Upcoming Solar Eclipse
- 02/01/1999 —Astronomy Updates with Brian Marsden and John Huchra, Harvard
“Directed Panspermia” by Francis Crick, Ph.D., and Leslie Orgel, Icarus 19,341-346 (1973): http://profiles.nlm.nih.gov/ps/access/SCBCCP.pdf
Icarus Int’l. Journal of Solar System Studies: http://icarus.cornell.edu/
Carbonaceous Chondrites: http://en.wikipedia.org/wiki/Carbonaceous_chondrite
Mars Science Laboratory: http://mars.jpl.nasa.gov/msl/
Osiris REx Asteroid Sample-to-Earth Mission:
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