ترم پاییز و بهار اختر زیست شناسی کودکان/ 1396-95

 جلسه ششم کلاس اختر زیست شناسی کودکان — 24 فروردین 1396

تاثیر بادهای ستاره ای و میدان مغناطیسی بر سیستم های حیاتمند و درحال تشکیل حیات

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ارائه مقاله علی اکبر گل پیچ (در قالب پوستر) با عنوان: 

The Effect Of Magnetic Field & Stellar Wind On Systems Contain Life And Forming Life

در هفتمین کنفرانس بین المللی اختفا و گرفت

(Haft Aseman Hafshejan, IAU, Iota/Me, and Shahr_kord University)

Meteorites and the RNA World: A Thermodynamic Model of Nucleobase Synthesis within Planetesimals

astrobiology.com:

Meteorites and the RNA World: A Thermodynamic Model of Nucleobase Synthesis within Planetesimals

The possible meteorite parent body origin of Earth's pregenetic nucleobases is substantiated by the guanine (G), adenine (A) and uracil (U) measured in various meteorites.

Cytosine (C) and thymine (T) however are absent in meteorites, making the emergence of a RNA and later RNA/DNA/protein world problematic.

We investigate the meteorite parent body (planetesimal) origin of all nucleobases by computationally modeling 18 reactions that potentially contribute to nucleobase formation in such environments. Out of this list, we identify the two most important reactions for each nucleobase and find that these involve small molecules such as HCN, CO, NH3, and water that ultimately arise from the protoplanetary disks in which planetesimals are built. The primary result of this study is that cytosine is unlikely to persist within meteorite parent bodies due to aqueous deamination. Thymine has a thermodynamically favourable reaction pathway from uracil, formaldehyde and formic acid, but likely did not persist within planetesimals containing H2O2 due to an oxidation reaction with this molecule.

Finally, while FT synthesis is found to be the dominant source of nucleobases within our model planetesimal, NC synthesis may still be significant under certain chemical conditions (e.g. within CR2 parent bodies). We discuss several major consequences of our results for the origin of the RNA world.

Ben K. D. Pearce, Ralph E. Pudritz

(Submitted on 22 Nov 2016)

Comments: published in Astrobiology, 21 pages, 10 figures (all coloured)

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Journal reference: 2016, Astrobiology, Vol. 16, Issue 11, pp. 853-872

DOI: 10.1089/ast.2015.1451

Cite as: arXiv:1611.07516 [astro-ph.EP] (or arXiv:1611.07516v1 [astro-ph.EP] for this version)

Submission history

From: Ben K. D. Pearce 

[v1] Tue, 22 Nov 2016 20:59:58 GMT (313kb,D)

https://arxiv.org/abs/1611.07516

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