Some 16,000 thousand feet up in Chile’s parched Atacama Desert, scientists have employed 66 antenna dishes to find an essential ingredient for life floating around a hot, young star system, 400 light years from Earth.
The dishes at the Atacama Large Millimeter Array, most of which are nearly 40-feet wide, picked up traces of a complex organic molecule called methyl isocyanate that is critical for building proteins in creatures here on Earth. Previously, scientists found a simple sugar floating around the infant three-star system with a not-so-simple name, IRAS 16293-2422.
“This star system seems to keep on giving! Following the discovery of sugars, we’ve now found methyl isocyanate,” write study co-authors Neil Ligterink and Audrey Coutens in a paper on the findings. “This family of organic molecules is involved in the synthesis of peptides and amino acids, which, in the form of proteins, are the biological basis for life as we know it.”
The researchers revealed their findings this week in two separate studies, both published in the journal Monthly Notices of the Royal Astronomical Society.
The star system is notably valuable because it’s so young. The stars are called protostars, which are still cosmic infants, gathering mass from the swirling cosmic storms around them. This gives scientists an opportunity view the happenings in a stellar nursery, similar to the environment that bore our sun and nine-ish planets. If the precursors to proteins were spawned in this young star system, perhaps they were born in our early solar system, too.
“We are particularly excited about the result because these protostars are very similar to the sun at the beginning of its lifetime, with the sort of conditions that are well suited for Earth-sized planets to form,” said Rafael Martín-Doménech and Víctor M. Rivilla, lead authors of one of the studies.
“By finding prebiotic molecules in this study, we may now have another piece of the puzzle in understanding how life came about on our planet.”
The massive, high-elevation antennas identify molecules like methyl isocyanate by detecting the light emitted from different astronomical objects and matter, whether they’re stars, planets, or giant clouds. Specifically, the 66 instruments at the Atacama Large Millimeter Array work in perfect synchrony to pick up radio signals from these interstellar bodies, which have long, spread-out wavelengths, falling on the opposite side of the electromagnetic spectrum from the visible light we can see.
In this case, ALMA’s antenna’s captured radio waves from IRAS 16293-2422, whose signals bore the chemical signatures of the organic molecule, methyl isocyanate.
Here on Earth, Ligterink found that methyl isocyanate can be made on icy particles in frigid environments — like the callous conditions in outer space. “This implies that this molecule — and thus the basis for peptide bonds — is indeed likely to be present near most new young solar-type stars,” explained Ligterink.
Although it might be difficult to remember the name IRAS 16293-2422, it could provide us the insight we need to understand how the stormy, chaotic cosmos provided our solar system — and perhaps many others — with the stuff of life.
Abstract: Detection of methyl isocyanate (CH3NCO) in a solar-typeprotostar: We report the detection of the prebiotic molecule CH3NCO in a solar-type protostar, IRAS16293-2422 B. A significant abundance of this species on the surface of the comet 67P/Churyumov-Gerasimenko has been proposed, and it has recently been detected in hot cores around high-mass protostars. We observed IRAS16293-2422 B with ALMA in the 90 GHz to 265 GHz range, and detected 8 unblended transitions of CH3NCO. From our Local Thermodynamic Equilibrium analysis we derived an excitation temperatureof 110±19 K and a column density of (4.0±0.3)×1015 cm−2, which results in an abundance of ≤(1.4±0.1)×10−10 with respect to molecular hydrogen. This implies a CH3NCO/HNCO and CH3NCO/NH2CHO column density ratios of ∼0.08. Our modelling of the chemistry of CH3NCO suggests that both ice surface and gas phase formation reactions of this molecule are needed to explain the observations.
Abstract: The ALMA-PILS survey: Detection of CH3NCO toward the low-mass protostar IRAS 16293-2422 and laboratory constraints on its formation: Methyl isocyanate (CH3NCO) belongs to a select group of interstellar molecules considered to be relevant precursors in the formation of larger organic compounds, including those with peptide bonds. The molecule has only been detected in a couple of high-mass protostars and potentially on comets. A formation route on icy grains has been postulated for this molecule but experimental evidence is lacking. Here we extend the range of environments where methyl isocyanate is found, and unambiguously identify CH3NCO through the detection of 43 unblended transitions in the ALMA Protostellar Interferometric Line Survey (PILS) of the low mass solar-type protostellar binary IRAS 16293-2422. The molecule is detected toward both components of the binary with a ratio HNCO/CH3NCO ∼4–12. The isomers CH3CNO and CH3OCN are not identified, resulting in upper abundance ratios of CH3NCO/CH3CNO > 100 and CH3NCO/CH3OCN > 10. The resulting abundance ratios compare well with those found for related N-containing species toward high-mass protostars. To constrain its formation, a set of cryogenic UHV experiments is performed. VUV irradiation of CH4:HNCO mixtures at 20 K strongly indicate that methyl isocyanate can be formed in the solid-state through CH3 and (H)NCO recombinations. Combined with gas-grain models that include this reaction, the solid-state route is found to be a plausible scenarioto explain the methyl isocyanate abundances found in IRAS 16293-2422.
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