北京時間8月10日消息,，據(jù)國外媒體報道,，美國宇航局的科學(xué)家通過對來自外太空的隕石進(jìn)行分析,，認(rèn)為地球生命可能起源于外太空,。這些隕石在墜落到地球上以前，已經(jīng)形成數(shù)億年,。
科學(xué)家發(fā)現(xiàn),，這些富含碳的碎片包含類似于DNA的一種重要組成成分的化合物,。檢測結(jié)果顯示，這些化學(xué)物質(zhì)的出現(xiàn)不能通過地球污染物的說法加以解釋,，這表明DNA可能起源于外太空,。美國科學(xué)家、優(yōu)秀的美國宇航局研究人員通過分析12塊隕石的化學(xué)成分,，獲得上述發(fā)現(xiàn),。該研究成果發(fā)表在美國《國家科學(xué)院院刊》（PNAS）上，他們在論文里說,，他們的發(fā)現(xiàn)具有“深遠(yuǎn)意義”,。
該研究負(fù)責(zé)人、馬里蘭州美國宇航局戈達(dá)德太空飛行中心的邁克爾-加拉漢博士說：“地球形成初期的隕石和彗星撞擊,，確實為地球帶來一些至關(guān)重要的生命組成成分,。”以前的研究發(fā)現(xiàn)，隕石蘊含著三種生命重要成分中的另外兩種,。它們分別是氨基酸（串在一起形成蛋白質(zhì)的“珠子”）和促使細(xì)胞產(chǎn)生隔膜“屏障”的化學(xué)物質(zhì),。DNA里的化學(xué)物質(zhì)是第三種。（生物谷 Bioon.com）
doi:10.1073/pnas.1106493108
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PMID:
Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases
Callahan, Michael ; Smith, Karen; Cleaves, James; Ruzicka, Josef; Stern, Jennifer; Glavin, Daniel .; House, Christopher ; Dworkin, Jason
All terrestrial organisms depend on nucleic acids (RNA and DNA), which use pyrimidine and purine nucleobases to encode geneticinformation. Carbon-rich meteorites may have been important sources of organic compounds required for the emergence of lifeon the early Earth; however, the origin and formation of nucleobases in meteorites has been debated for over 50 y. So far,the few nucleobases reported in meteorites are biologically common and lacked the structural diversity typical of other indigenousmeteoritic organics. Here, we investigated the abundance and distribution of nucleobases and nucleobase analogs in formicacid extracts of 12 different meteorites by liquid chromatography–mass spectrometry. The Murchison and Lonewolf Nunataks 94102meteorites contained a diverse suite of nucleobases, which included three unusual and terrestrially rare nucleobase analogs:purine, 2,6-diaminopurine, and 6,8-diaminopurine. In a parallel experiment, we found an identical suite of nucleobases andnucleobase analogs generated in reactions of ammonium cyanide. Additionally, these nucleobase analogs were not detected aboveour parts-per-billion detection limits in any of the procedural blanks, control samples, a terrestrial soil sample, and anAntarctic ice sample. Our results demonstrate that the purines detected in meteorites are consistent with products of ammoniumcyanide chemistry, which provides a plausible mechanism for their synthesis in the asteroid parent bodies, and strongly supportsan extraterrestrial origin. The discovery of new nucleobase analogs in meteorites also expands the prebiotic molecular inventoryavailable for constructing the first genetic molecules.
