Quest for life-forming chemicals

Is there a trend emerging from space science? Were certain programs focused on those trends? Are space projects and goals aimed in a certain direction...finding life, remnants of previous life, elements to form new life in the universe? How many times have we heard from the scientists of possible water on Mars, Saturn's moon Titan is Earth-like and a possible environment for life, elemental life-forming molecules found in various areas of the universe. Is there an underlying desire to find intelligent comrades in the universe, an unconscious desire to thwart man's uniqueness--a blow to theology, to offer solace that we are not alone or were not alone or life is possible elsewhere?

Two aldehyde molecules [propanol and propenal], formaldehyde, glycolaldehyde, and polycyclic aromatic hydrocarbons are becoming more evident in space and are the building blocks of life. Those two aldehyde molecules are interesting for at least two reasons. First, they were discovered recently in an interstellar dust cloud in an area known as Sagittarius B2 about 26 million light years away and provide clues to molecule evolution by the simple hydrogen addition reactions process. They are rare for most molecules are of the five atom variety and there is a lot of speculation as to the formation of the larger molecules. Their significance is that it leads to models regarding the origin of the formation of more complex molecules and to the potential formation of biological life forms--in particular as to whether the more complex molecules are produced in space or of a terrestrial origin. Secondly, the methodology of detecting these molecules is fascinating and employs the sensitivity of a radio telescope--Robert C. Byrd Green Bank Telescope (GBT). This radio telescope is able to identify specific radio emission signatures of various molecules as they rotate and change energy frequencies--molecular fingerprints.

Astrobiology Magazine:

And formaldehyde...Ohio State University scientists claim that there is more formaldehyde in the universe than expected--some 100 times more. Five molecules of formaldehyde yield ribose [reducing sugars]--not far from deoxyribose which are building blocks of DNA and RNA.

The preservative formaldehyde is made in deep space from carbon dioxide mainly, but recent research proposes that formaldehyde may form ten times more amidst interstellar dust than supposed previously.

Scientists at Ohio State University have found that a formaldehyde-based chemical is 100 times more common in parts of our galaxy than can be explained.

The finding could change ideas about how organic molecules form in the universe, and how those molecules' critical interaction with dust causes stars and planets to form.

The scientists compared the results of experiments from an international team of chemists to telescopic measurements of the amount of methyl formate -- a product of alcohol and formaldehyde -- in the swirling dust clouds that dot our Milky Way galaxy. On Earth, methyl formate is commonly used as an insecticide.

Based on telescope data, if the gaseous methyl formate condensed into liquid form, a typical dust cloud would contain a thousand trillion trillion gallons of the chemical.

Interstellar dust clouds contain the chemical seeds of new stars and planetary systems, explained Eric Herbst, Distinguished Professor of Mathematical and Physical Sciences at Ohio State. Most people are probably familiar with the dust cloud known as the Horsehead Nebula in the constellation Orion.

While scientists have long known that hydrogen is the most common chemical element in the universe, just 10 years ago Herbst -- a professor of physics, chemistry, and astronomy -- and his colleagues discovered that there were also large quantities of alcohol in dust clouds in space. The presence of methyl formate suggests that other molecules may play a more prominent role in star and planet formation than scientists ever suspected.

"Even using our best models of interstellar chemistry, we still don't fully understand how these molecules could have formed," Herbst said. "Clearly, something else is going on."

Herbst reported the new results June 23 at the International Symposium on Molecular Spectroscopy in Columbus.

Three groups of chemists from the United States, Canada, and Norway had previously conducted laboratory experiments to determine how alcohol and other molecules produce methyl formate. Herbst and Ohio State postdoctoral researcher Helen Roberts used that data to construct a new model of how such reactions happen in space, and then used the model to predict how much methyl formate would be found in the typical interstellar dust cloud.

Next, the Ohio State scientists consulted the radio spectrum of the dust clouds, which gives them the unique chemical signatures of the different molecules floating inside.

The spectra showed that the average ratio of hydrogen molecules to molecules of methyl formate was a billion to one. But the model that Herbst and Roberts derived had predicted only a fraction of that amount.

"We calculated the ratio to be 100 billion to one, so the model must be deficient," Herbst said.

Scientists will have to refine the models before they can truly know how stars and planets form, he said.

According to accepted theory, gas molecules floating in these clouds must join and nuclear reactions must begin before stars can form. Dust particles are key to the process because they provide a surface for reactions to take place.

Among their future goals, Herbst, Roberts, and their colleagues want to determine exactly what space dust is made of and what the surface texture is like, since both would affect chemical reactions -- a task that amounts to studying individual dust grains thousands of light years away.

Modeling such large, complex systems requires a great deal of computing power, and measuring the actual amounts of chemicals in these faraway clouds is difficult. Herbst said that supercomputers and telescopes are just beginning to advance to the point where such things are possible. In the future, he would like to form a consortium of researchers in molecular astronomy to pool ideas and resources.

And Glycolaldehyde [simple sugar variety]...may be just more evidence for the formation of life in the universe. This chemical was discovered by Jan M. Hollis, Frank J. Lovas, and Philip R. Jewell at the National Science Foundation's 12 Meter Telescope [Kitt Peak, Arizona.] nearly 26,000 light years away close to the center of the Milky Way Galaxy in an interstellar cloud [Sagittarius B2]. Such a hostile environment can accommodate the building blocks of life.

Spaceflight Now:

"Sugar in space provides clue to origin of life"

September 21st, 2004

Astronomers using the National Science Foundation's giant Robert C. Byrd Green Bank Telescope (GBT) have discovered a frigid reservoir of simple sugar molecules in a cloud of gas and dust some 26,000 light-years away, near the center of our Milky Way Galaxy. The discovery suggests how the molecular building blocks necessary for the creation of life could first form in interstellar space.

The astronomers detected the 8-atom sugar molecule glycolaldehyde in a gas-and-dust cloud called Sagittarius B2. Such clouds, often many light-years across, are the raw material from which new stars and planets are formed. The astronomers detected the same molecule in a warmer part of that cloud in 2000, but the new detection shows that the sugar exists at an extremely low temperature -- only 8 degrees above absolute zero, the temperature at which all molecular motion stops. The cold glycolaldehyde detections were surprisingly strong when compared to the original detections and indicate that a considerable quantity of this simple interstellar sugar exists at extremely low temperatures.

Glycoaldehyde is composed of 2 carbon atoms, 2 oxygen atoms and 4 hydrogen atoms and is called a 2-carbon sugar. Glycolaldehyde can react with a 3-carbon sugar to produce a 5-carbon sugar called ribose. Ribose molecules form the backbone structure of the molecules DNA and RNA, which carry the genetic code of living organisms.

On Earth, most chemical reactions occur in liquid water. Conditions are quite different in interstellar space, and most of the complex molecules appear to form on or under the surfaces of tiny dust grains. In this scenario, smaller molecules such as water, formaldehyde, methane, ammonia, carbon dioxide, or methanol, coat the surfaces and interiors of dust grains in the clouds. When a shock wave, caused by the infall or outflow of material in the star-formation process, hits the dust grains, it provides the energy to assemble more-complex molecules from the simpler ones, and also to free the newly-formed molecules from the dust grains. Once the shock has passed, the molecules cool into a cold, thin gas.

Although the chemistry on Earth and in interstellar clouds is much different, the results can be very similar. This and other recent studies show that prebiotic chemistry -- the formation of the molecular building blocks necessary for the creation of life -- occurs in interstellar clouds long before that cloud collapses to form a new solar system with planets. "Many of the interstellar molecules discovered to date are the same kinds detected in laboratory experiments specifically designed to synthesize prebiotic molecules. This fact suggests a universal prebiotic chemistry," said Jan M. Hollis of NASA's Goddard Space Flight Center in Greenbelt, MD. This suggests that the molecular building blocks for the creation of life on a new planet might get a head start in the dust of interstellar clouds.

The actual formation of a planetary system is such a hot process that any prebiotic molecules would likely be destroyed. However, this study has shown that such molecules may form in very cold regions following the passage of a shock wave. Such conditions might be typical of the outer regions of a young solar system following the star-formation process. A repository of prebiotic molecules might exist in these outer regions, which is also where comets are formed, the scientists said. It has long been suggested that a collision with a comet or an encounter with the passing tail of a comet might "seed" a young planet with prebiotic material.

Hollis worked with Philip Jewell of the National Radio Astronomy Observatory in Green Bank, WV, Frank Lovas of the National Institute of Standards and Technology in Gaithersburg, MD, and Anthony Remijan of NASA's Goddard Space Flight Center. The scientists reported their findings in the September 20 issue of the Astrophysical Journal Letters.

The discovery of the cold glycolaldehyde was made by detecting faint radio emission from the molecules. Molecules rotate end-for-end. When they change from a higher rotational energy level to a lower energy level, they emit radio waves at precise frequencies. Conversely, they can absorb radio waves at specific frequencies and change from a lower rotational energy level to a higher one. A set of frequencies emitted or absorbed by a particular molecule forms a unique "fingerprint" identifying that molecule. The cold glycolaldehyde was identified both by emission from the molecules and by absorption of radio waves emitted by a background source, all between 13 GHz and 22 GHz in frequency.

"The large diameter and great precision of the GBT made this discovery possible, and also holds the promise of discovering additional new complex interstellar molecules," Jewell said. The GBT, dedicated in 2000, is the world's largest fully- steerable radio-telescope antenna. Its dish reflector has more than 2 acres of signal-collecting area.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

And the plot, rather the "soup of life", thickens with the recent discovery by the Spitzer Space Telescope of "polycyclic aromatic hydrocarbons".


NASA:

"NASA's Spitzer Space Telescope has found the ingredients for life all the way back to a time when the universe was a mere youngster"

Using Spitzer, scientists have detected organic molecules in galaxies when our universe was one-fourth of its current age of about 14 billion years. These large molecules, known as polycyclic aromatic hydrocarbons, are comprised of carbon and hydrogen. The molecules are considered to be among the building blocks of life.

These complex molecules are very common on Earth. They form any time carbon-based materials are not burned completely. They can be found in sooty exhaust from cars and airplanes, and in charcoal broiled hamburgers and burnt toast.

The molecules, pervasive in galaxies like our own Milky Way, play a significant role in star and planet formation. Spitzer is the first telescope to see these molecules so far back in time.

"This is 10 billion years further back in time than we've seen them before," said Dr. Lin Yan of the Spitzer Science Center at the California Institute of Technology in Pasadena, Calif. Yan is lead author of a study to be published in the August 10 issue of the Astrophysical Journal. Previous missions -- the Infrared Astronomical Satellite and the Infrared Space Observatory -- detected these types of galaxies and molecules much closer to our own Milky Way galaxy. Spitzer's sensitivity is 100 times greater than these previous infrared telescope missions, enabling direct detection of organics so far away.

Since Earth is approximately four-and-a-half billion years old, these organic materials existed in the universe well before our planet and solar system were formed and may have even been the seeds of our solar system. Spitzer found the organic compounds in galaxies where intense star formation had taken place over a short period of time. These "flash in the pan" starburst galaxies are nearly invisible in optical images because they are very far away and contain large quantities of light-absorbing dust. But the same dust glows brightly in infrared light and is easily spotted by Spitzer.

Spitzer's infrared spectrometer split the galaxies' infrared light into distinct features that revealed the presence of organic components. These organic features gave scientists a milepost to gauge the distance of these galaxies. This is the first time scientists have been able to measure a distance as great as 10-billion light years away using the spectral fingerprints of polycyclic aromatic hydrocarbons.

"These complex compounds tell us that by the time we see these galaxies, several generations of stars have already been formed," said Dr. George Helou of the Spitzer Science Center, a co-author of the study. "Planets and life had very early opportunities to emerge in the universe."

And also from NASA:

"Scientists find clues that the path leading to the Origin of Life begins in Deep Space"

Moffett Field, California.-- Duplicating the harsh conditions of cold interstellar space, scientists from NASA's Ames Research Center have shown that nitrogen containing aromatic molecules, chemical compounds that could be important for life's origin, are widespread throughout space.

Combining laboratory experiments with computer simulations, this team had earlier shown that complex organic molecules known as polycyclic aromatic hydrocarbons (PAHs) are widespread throughout space. PAHs, large, flat, chicken-wire shaped molecules made up of hydrogen and carbon are extremely stable and can withstand the hostile radiation environment of interstellar space. The Ames team showed that PAHs are responsible for the mysterious infrared radiation that astronomers first called the Unidentified Infrared Emission. NASA's Spitzer Space Telescope, an instrument of unprecedented sensitivity, has now detected the PAH tell-tale signature throughout our galaxy the Milky Way and in galaxies very far away, galaxies nearly as old as the Universe itself. Now the Ames team has found that these PAHs contain nitrogen, a key biochemical element. Doug Hudgins, the lead author of the study, points out "Not only are nitrogen containing aromatic hydrocarbons the information carrying molecules in the DNA and RNA that make up all living matter as we know it, they are found in many biologically important species. For example, caffeine and the main ingredient in chocolate are among these kinds of molecule. Seeing their signature across the Universe tells us they are accessible to young, habitable planets just about everywhere."

This is the first direct evidence for the presence of complex, prebiotically important, biogenic compounds in space and brings us a step closer to assessing if life's origin on Earth may have had a helping hand from infalling stardust. The bulk of the astronomical evidence points to the formation of these nitrogen containing PAHs in the winds of dying stars which inject them into interstellar space. Eventually they become incorporated into the clouds of material that give birth to stars and planets. Freshly formed planets continue to collect infalling material (dust, asteroids, meteorites, and comets) from the star formation process and life on Earth is thought to have emerged from this primordial chemical soup.

The most common scientific theory for the origin of life on Earth is that somewhere in the vast, but simple, chemical resources available on the early Earth, conditions favored the formation of more complex chemical compounds and chemical processes which eventually led to life. However, this theory was conceived at a time when it was thought space was barren of complex organics because interstellar radiation is too harsh, the distances too great, and violent shocks too frequent to support complex chemistry, let alone survival of large molecules and their transport to planetary surfaces. In sharp contrast to that picture, this new work shows that the early chemical steps believed to be important for the origin of life do not require a previously formed planet to occur. Instead, some of the chemicals are already present throughout space long before planet formation occurs and, if they land in a hospitable environment, can help jump-start the origin of life.

The NASA Ames team developed the techniques to measure the PAH infrared signature under conditions found in space - no small feat. While on Earth these compounds are in the solid form; in space they are in the gas, under vacuum, electrically charged and very cold (near absolute zero -441oF/ -263oC). "The terrestrial PAH IR fingerprint hardly resembles the emission from space. However, when we prepare the PAHs as they are in space the IR signature changes dramatically and the match is pretty good" said Lou Allamandola, space scientist and team leader. It was this good overall match that largely established the acceptance of PAHs in space and justified digging deeper and bringing powerful new tools to bear on the problem. Chief among these is computational chemistry. "Given Ames is NASA's Information Technology Center for Excellence, it was a natural to see if we could calculate the infrared signature of these very complex molecules. It had never been done before and, now with the lab data available, we could test and sharpen the accuracy of our methods" said Charles Bauschlicher, a renowned computational chemist. "Now that we know the computational methods work very well, the great advantage computational chemistry brings to this effort is the ability to calculate the IR spectrum of PAHs and related species for which there is no lab counterpart. You can imagine that stars don't eject only chemicals that can be put in a bottle and stored on a shelf. We can now calculate the spectra of those very elusive molecules" stressed Bauschlicher. This ability is key to the new work reported here.

While the PAH model appeared to satisfy many observations made through most of the 90's, the higher quality IR spectra that were beamed back to Earth from The Infrared Space Observatory, ISO, posed new challenges. In analyzing these spectra, Belgian astronomer Els Peeters found small but real mismatches with the Ames spectra. "We measured the complete infrared spectra of over 55 different astronomical objects, many which couldn't be detected before. We found that none of the spectra in the Ames database could reproduce the regular changes we saw that occurred between very old interstellar regions and very young astronomical objects known as planetary nebulae," said Peeters. "That difference showed something important was missing in the Ames dataset and that something told us about PAH evolution" explained Peeters.

"This was about the time we realized that chemically, a nitrogen atom could easily replace a carbon in a PAH's hexagonal skeleton" recalled Hudgins, "but we didn't have a clue as to how that might alter the PAH spectrum." This was also the time when experimental physical chemist and Oklahoman Andrew Mattioda joined the group. "Those were exciting days" Mattioda remembered, "the PAH spectra we had were being used as new tools to analyze regions thousands of light years away and, incredibly, new observations were giving us feedback on the structures of these distant molecules and conditions in the astronomical objects themselves. We geared up to measure the spectra of all the nitrogen containing PAHs (PANHs) we could find, but there weren't many and they are much smaller than those we believe are in space. There are probably hundreds of different PANHs in space and we only had six or seven of the smaller ones." Ultimately, Mattioda's experiments showed that the simple PANHs could not resolve the problem Peeters uncovered.

This was when the computational power came to the fore. Bauschlicher determined the spectra of a variety of species involving PAHs to understand the changes Peeters had found. "Because I can compute the spectra of PAHs much larger than anything that has been synthesized and also vary the placement of nitrogen within these large molecules, something impossible for the lab, we can now investigate a very large number of PAH varieties and sizes." Bauschlicher explained. "With this we have shown we can reproduce both the range in spectral shift Els measured and the relative intensities she found by incorporating N deep into the PAH skeleton" he explained further.

This discovery is profound at several levels. "First, this resolves part of a longstanding mystery about the distribution of nitrogen in space, second, PANHs have signatures in the optical and radio wavelengths that can account for unexplained astronomical phenomena and third, these compounds are of biogenic interest" summed Hudgins. "Most people will take notice of their possible role in the origin of life, the point in our history when chemistry became biology, but there are other serious implications as well" he continued.

There are hundreds if not thousands of these species in space and it is beginning to look like these types of compounds are strikingly similar to many of those brought to Earth today by infalling meteorites and their smaller cousins, the interplanetary dust particles. Every year more than a hundred tons of extraterrestrial stuff falls on the Earth, and much of it is in the form of organic material. In the early life of our Solar System, before the debris from its formation was fully cleared away, these materials were deposited on the Earth in far greater quantities than we see today. Thus, much of the organic material found on the primordial Earth likely included a strong dose of interstellar PANHs.

Allamandola reiterated, "The spell is now breaking that interstellar chemistry is only a chemistry of relatively small and simple molecules. Twenty years ago the notion of abundant, gas phase, polycyclic aromatic hydrocarbons anywhere in interstellar space was considered impossible. Now we know better. PANHs/PAHs dwarf all other known . Infrared image of spiral galaxy M-81 taken by the Spitzer Space Telescope. The red traces the emission from PANHs. interstellar molecules in size and, as a class, they are more abundant than all other known interstellar polyatomic molecules combined. We are only seeing the tip of the iceberg in terms of extraterrestrial molecular complexity. Spitzer has detected the PAH IR signature across the Universe, even back to only a few billion years after the Big Bang. When the Universe is looked at through PAH filtered glasses it is clear that PAHs are indeed everywhere and we live in a molecular Universe."

And the bottom line is this: Ashes to ashes, dust to dust; we come from dust; we return to dust--we are "star stuff".

"In the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou art, and unto dust shalt thou return."--Genesis 3:19