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After A team of NASA exobiology researchers revealed today organic chemicals that play a crucial role in the chemistry of life are common in space.
"Our work shows a class of compounds that is critical to biochemistry is prevalent throughout the universe," said Douglas Hudgins, an astronomer at NASA's Ames Research Center, Moffett Field, Calif. He is principal author of a study detailing the team's findings that appears in the Oct. 10 issue of the Astrophysical Journal.
"NASA's Spitzer Space Telescope has shown complex organic molecules called polycyclic aromatic hydrocarbons (PAHs) are found in every nook and cranny of our galaxy. While this is important to astronomers, it has been of little interest to astrobiologists, scientists who search for life beyond Earth. Normal PAHs aren't really important to biology," Hudgins said. "However, our work shows the lion's share of the PAHs in space also carry nitrogen in their structures. That changes everything."
"Much of the chemistry of life, including DNA, requires organic molecules that contain nitrogen," said team member Louis Allamandola, an astrochemist at Ames. "Chlorophyll, the substance that enables photosynthesis in plants, is a good example of this class of compounds, called polycyclic aromatic nitrogen heterocycles, or PANHs. Ironically, PANHs are formed in abundance around dying stars. So even in death, the seeds of life are sewn," Allamandola said.
"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 (Figure 2). Seeing their signature across the Universe tells us they are accessible to young, habitable planets just about everywhere."
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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.
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.
Originally posted by Zipdot
It is posited that silicon molecules are too unstable to allow for life. Carbon is the element of life as we know it and should be (and is) our focus in elemental life studies. This is not a result of short-sightedness, it is due to our prudence.
Originally posted by nukunuku
well somehow, i knew this waaay before NASA did, and i dont have a multibillion $ budget