Observations of Interstellar Formamide: Availability of a Prebiotic Precursor in the Galactic Habitable Zone

Abstract

We conducted a study on interstellar formamide, NH 2 CHO, toward star-forming regions of dense molecular clouds, using the telescopes of the Arizona Radio Observatory (ARO). The Kitt Peak 12 m antenna and the Submillimeter Telescope (SMT) were used to measure multiple rotational transitions of this molecule between 100 and 250 GHz. Four new sources of formamide were found [W51M, M17 SW, G34.3, and DR21(OH)], and complementary data were obtained toward Orion-KL, W3(OH), and NGC 7538. From these observations, column densities for formamide were determined to be in the range of 1.1 · 10 12 to 9.1 · 10 13 cm -2 , with rotational temperatures of 70-177 K. The molecule is thus present in warm gas, with abundances relative to H 2 of 1 · 10 -11 to 1 · 10 -10 . It appears to be a common constituent of star-forming regions that foster planetary systems within the galactic habitable zone, with abundances comparable to that found in comet Hale-Bopp. Formamide's presence in comets and molecular clouds suggests that the compound could have been brought to Earth by exogenous delivery, perhaps with an infall flux as high as *0.1 mol/km 2 /yr or 0.18 mmol/m 2 in a single impact. Formamide has recently been proposed as a single-carbon, prebiotic source of nucleobases and nucleic acids. This study suggests that a sufficient amount of NH 2 CHO could have been available for such chemistry.

On the Formation of Amide Polymers via Carbonyl–amino Group Linkages in Energetically Processed Ices of Astrophysical Relevance

“…The formamide molecule (HCONH 2 ) as detected in the interstellar medium (ISM; Gottlieb et al 1973;Hollis et al 2006;Halfen et al 2011;Adande et al 2013) represents the simplest molecule carrying the amide (peptide) bond (Figure 1). Very recently, Jones et al (2011) elucidated the formation mechanism of formamide in astrophysically relevant ices exposed to energetic electrons via the radical-radical recombination of formyl (HCO) with the amidogen radical (NH 2 ) inside astrophysically relevant ices at 10 K. The next homologue molecule in this series-urea (CO (NH 2 ) 2 )-was also detected in processed ices online and in situ, exploiting photoionization of the subliming molecules during the temperature programmed desorption (TPD) phase via tunable vacuum ultraviolet (VUV) light and by detecting the parent ion through a reflectron time-of-flight mass spectrometer (PI-ReTOF-MS; Förstel et al 2015a) It is also well established that amino acids (Bernstein et al 2002;Munoz Caro et al 2002;Elsila et al 2007;Chen et al 2008;Hudson et al 2008) and their formal condensation products-dipeptides-as complex as Glycylglycine (Gly-Gly) and LeucylAlanine (Leu-Ala) can be synthesized abiotically in energetically processed ices ; Figure 1).…”

“…Considering the identification of biorelevant molecules, formamide (HCONH 2 ) was first detected toward Sgr A and Sgr B2 by Gottlieb et al (1973) and subsequently confirmed by Hollis et al (2006), Halfen et al (2011), and Adande et al (2013). Halfen et al determined fractional abundances in the range from 5.3×10…”

Impact synthesis of the RNA bases

“…Astronomers have recently reported its presence in our solar system found within the atmospheres of comets (6), and since the 1970s, formamide has been detected in multiple regions in the interstellar medium (7). The known chemistry and ubiquity of formamide has made it an attractive primordial feedstock compound for the production of many prebiotic molecules (8).…”

Meteorite-catalyzed syntheses of nucleosides and of other prebiotic compounds from formamide under proton irradiation

“…FA is a ubiquitous molecule in the universe. It has been detected in galactic centers (Sgr A and Sgr B), in star-forming regions of dense molecular clouds, in high-mass young stellar objects, in the interstellar medium and in comets and satellites (5)(6)(7)(8)(9)(10)(11)(12)(13)(14).With the appropriate mineral as catalyst, different ensembles of intermediates of genetic and metabolic apparatuses are simultaneously synthesized from FA under thermal conditions (i.e., by heating liquid FA between 333 and 453 K at room pressure). DNA and RNA components (15-21), amino acids (22, 23), sugars (24), and carboxylic acids (25, 26) have been obtained.…”

“…FA is a ubiquitous molecule in the universe. It has been detected in galactic centers (Sgr A and Sgr B), in star-forming regions of dense molecular clouds, in high-mass young stellar objects, in the interstellar medium and in comets and satellites (5)(6)(7)(8)(9)(10)(11)(12)(13)(14).…”