Precursors of the RNA World in Space: Detection of (Z)-1,2-ethenediol in the Interstellar Medium, a Key Intermediate in Sugar Formation

We present the first detection of (Z)-1,2-ethenediol, (CHOH)₂, the enol form of glycolaldehyde, in the interstellar medium toward the G+0.693-0.027 molecular cloud located in the Galactic Center. We have derived a column density of (1.8 ± 0.1) × 10¹³ cm^-2, which translates into a molecular abundance with respect to molecular hydrogen of 1.3 × 10^-10. The abundance ratio between glycolaldehyde and (Z)-1,2-ethenediol is ~5.2. We discuss several viable formation routes through chemical reactions from precursors such as HCO, H₂CO, CHOH, or CH₂CHOH. We also propose that this species might be an important precursor in the formation of glyceraldehyde (HOCH₂CHOHCHO) in the interstellar medium through combination with the hydroxymethylene (CHOH) radical.