BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Cometary Delivery of Hydrogen Cyanide to the Early Earth  - Zoe To
 dd\, University of Washington\, Sagan Fellow
DTSTART:20210126T130000Z
DTEND:20210126T140000Z
UID:TALK155875@talks.cam.ac.uk
CONTACT:Paul B. Rimmer
DESCRIPTION:Delivery of water and organics by asteroid and comet impacts m
 ay have influenced prebiotic chemistry on the early Earth. Some recent pre
 biotic chemistry experiments emphasize hydrogen cyanide (HCN) as a feedsto
 ck molecule for the formation of sugars\, ribonucleotides\, amino acids\, 
 and lipid precursors. Here\, we assess how much HCN originally contained i
 n a comet would survive impact\, using parametric temperature and pressure
  profiles together with a time-dependent chemistry model. We find that HCN
  survival mainly depends on whether the impact is hot enough to thermally 
 decompose H2O into reactive radicals\, and HCN is therefore rather insensi
 tive to the details of the chemistry. In the most favorable impacts (low i
 mpact angle\, low velocity\, small radius)\, this temperature threshold is
  not reached\, and intact delivery of HCN is possible. We estimate the glo
 bal delivery of HCN during a period of Early and Late Heavy Bombardment of
  the early Earth\, as well as local HCN concentrations achieved by individ
 ual impacts. In the latter case\, comet impacts can provide prebiotically 
 interesting HCN levels for thousands to millions of years\, depending on p
 roperties of the impactor and of the local environment.
LOCATION:ONLINE - Details to be sent by email
END:VEVENT
END:VCALENDAR