BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:(Universal Life) Consequences of Heavy Bombardment Periods on Che mistry of the Early Earth - Martin Ferus (Prague) DTSTART:20170201T160000Z DTEND:20170201T170000Z UID:TALK69715@talks.cam.ac.uk CONTACT:Ed Gillen DESCRIPTION:As the Sun formed from its molecular cloud\, it was accompanie d by a disk of material that consisted of gas and small dust particles. Ov er a few tens of millions of years\,  these dust particles accumulated an d formed the planets that we see today. This process occurred in several s tages in the terrestrial planet zone\, eventually culminating in massive\, potentially moon-forming impacts on the proto-Earth.(1) Then\, following the solidification of the Moon around 4.5 Ga\, the initially heavy impacto r flux declined(2) and increased again during the Late Heavy Bombardment ( LHB) some 4-3.85 Ga.(2) Best models for the origin of the LHB link it to a dynamic instability in the outer solar system (the so-called Nice model (3)\,(4))\, when Jupiter’s orbit changed as a result of close encounters with ice giants and small cometary bodies. These changes resulted in the release of impactors from their previously stable asteroidal and cometary reservoirs. The synthesis of observation and theoretical constraints indic ates that the impactor flux on the Earth was around 10 times higher at the LHB than in the period immediately preceding the LHB and that this flux slowly decayed afterwards.(5)\,(6)\,(7) At the peak\, the LHB most likely involved an impact frequency of 109 tons of material per year.(5) The typi cal impact speeds are estimated to have increased from around 9 to 21 km /s once the LHB began. The ratio of the gravitational cross-sections of Ea rth and the Moon is found to be approximately 17:1. Thus\, for every lunar basin\, such as Orientale or Imbrium\, approximately 17 basins should hav e formed on the Earth.(8) \n\nSuch a huge impact activity also had extensi ve implications for the evolution of early Earth:(9) the atmosphere was pa rtly eroded and transformed\,(10)\,(11) and the hydrosphere was enriched b y water.(12)\,(13) Crucially\, these impact-related processes most likely also contributed to the transformation of biomolecules and their precursor s on Earth’s surface\, which would have relevant consequences on the ori gin of life.(14)\,(15)  Our recent findings demonstrate that extraterrest rial impacts\, which were an order of magnitude more abundant during the l ate heavy bombardment period than before and after\, could not only destro y the existing ancient life forms\, but they could also contribute to the creation of biogenic molecules. In our pioneering works\,(16) we simulated the high-energy synthesis of aminoacids in simple mixtures of molecular gases with compositions (CO2–N2–H2O and CO–N2–H2O) and total press ure close to that of the Earth´s early atmospheres. Glycine\, alanine\, s erine and asparagine were found using HPLC analytical technique. In subseq uent experiments\, we demonstrated synthesis of all the RNA canonical nucl eic bases from formamide during such an impact of an extraterrestrial body .(17) Again\, high-power laser has been used to induce the dielectric brea kdown of the plasma produced by the impact. The experimental results toget her with plasma chemistry models and quantum chemistry calculations demons trate that initial dissociation of the formamide molecule produces a large amount of highly reactive CN and NH radicals\, which could further react with formamide to produce adenine\, guanine\, cytosine\, and uracil. Also\ , according to the optical spectra\, LIDB plasma surely contains excited c arbon and nitrogen ions\, atoms and molecules\, and CN radical (also C2 an d C3).(18) We also show that sugars can be synthetized from formaldehyde i n high energy environment of the shock wave plasma together with basic mol ecule necessary for catalytic conversion of formaldehyde to sugars in such environments – glycoladehyde (condensation reactions over borates etc.) .(19) We can conclude that high energy chemistry serves as a powerful trig ger of biomolecules synthesis and it possibly contributed to origin of lif e on early Earth. \n\nReferences\n\n1. Canup RM\, Asphaug E (2001) Ori gin of the Moon in a giant impact near the end of the Earth’s formation. Nature 412:708–712.\n\n2. Koeberl C\, Reimold WU\, McDonald I\, Rosing M (2000) in IMPACTS AND THE EARLY EARTH\, LECTURE NOTES IN EARTH SCIENCES .\, ed Gilmour\, I and Koeberl C (SPRINGER-VERLAG BERLIN\, HEIDELBERGER PL ATZ 3\, D-14197 BERLIN\, GERMANY)\, pp 73–97.\n\n3. Tsiganis K\, Gomes R\, Morbidelli A\, Levison HF (2005) Origin of the orbital architecture of the giant planets of the Solar System. Nature 435:459–461.\n\n4. Nesvo rny D\, Morbidelli A (2012) Statistical Study of the Early Solar System’ s Instability with Four\, Five\, and Six Giant Planets. Astron J 144.\n5. Koeberl C (2006) Impact processes on the early Earth. Elements 2:211–21 6.\n\n6. Geiss J\, Rossi AP (2013) On the chronology of lunar origin and evolution Implications for Earth\, Mars and the Solar System as a whole. A stron Astrophys Rev 21.\n\n7. Morbidelli A\, Marchi S\, Bottke WF\, Kring DA (2012) A sawtooth-like timeline for the first billion years of lunar b ombardment. EARTH Planet Sci Lett 355:144–151.\n\n8. Bottke WF et al. ( 2012) An Archaean heavy bombardment from a destabilized extension of the a steroid belt. Nature 485:78–81.\n9. Lunine JI (2006) Physical condition s on the early Earth. Philos Trans R Soc B-BIOLOGICAL Sci 361:1721–1731. \n\n10. De Niem D\, Kuehrt E\, Morbidelli A\, Motschmann U (2012) Atmosph eric erosion and replenishment induced by impacts upon the Earth and Mars during a heavy bombardment. Icarus 221:495–507.\n\n11. Ferus M\, Matulk ova I\, Juha L\, Civis S (2009) Investigation of laser-plasma chemistry in CO-N-2-H2O mixtures using O-18 labeled water. Chem Phys Lett 472:14–18. \n\n12. Morbidelli A et al. (2000) Source regions and timescales for the delivery of water to the Earth. Meteorit Planet Sci 35:1309–1320.\n\n13. Cavosie AJ\, Valley JW\, Wilde SA (2005) Magmatic delta O-18 in 4400-390 0 Ma detrital zircons: A record of the alteration and recycling of crust i n the Early Archean. EARTH Planet Sci Lett 235:663–681.\n\n14. Chyba C\ , Sagan C (1992) Endogenous Production\, Exogenous Delivery and Impact-Sho ck Synthesis of Organic Molecules - an Inventory for the Origin of Life. N ature 355:125–132.\n\n15. Chyba CF\, Thomas PJ\, Brookshaw L\, Sagan C (1990) Cometary Delivery of Organic Molecules to the Early Earth. Science (80- ) 249:366–373.\n\n16. Civis S\, et al. (2004) Amino acid formation induced by high-power laser in CO2/CO-N-2-H2O gas mixtures. Chem Phys Let t 386(1–3):169–173.\n\n17. Ferus M\, et al. (2015) High-energy chemis try of formamide: A unified mechanism of nucleobase formation. Proc Natl A cad Sci 112(3):657–662.\n\n18. Ferus M\, et al. (2016) Small Radicals a nd they Role in Prebiotic Plasma Chemistry - Network in Reduction Atmosphe res. Phys Chem Chem Phys:In Review Process.\n\n19. Civis S\, et al. (2016 ) TiO2-catalyzed synthesis of sugars from formaldehyde in extraterrestrial impacts on the early Earth. Sci Rep 6. doi:10.1038/srep23199.\n LOCATION:Sackler Lecture Theatre\, IoA END:VEVENT END:VCALENDAR