Life on Earth ‘may have begun on Mars’

Mars could be the origin of minerals needed to create life (Picture: AP)

Life on Earth may have started on Mars and been blasted onto our planet by meteorites or volcanic eruptions, a major scientific conference has heard.

An element believed to be crucial to the origin of life would only have been available on the surface of the Red Planet, it is claimed.

Geochemist Professor Steven Benner argues that the ‘seeds’ of life probably arrived on Earth in meteorites or via volcanic eruptions.

As evidence he points to the oxidised mineral form of the element molybdenum, thought to be a catalyst that helped organic molecules develop into the first living structures.

‘It’s only when molybdenum becomes highly oxidised that it is able to influence how early life formed,’ said Professor Benner, from The Westheimer Institute for Science and Technology in the United States.

‘This form of molybdenum couldn’t have been available on Earth at the time life first began, because three billion years ago the surface of the Earth had very little oxygen, but Mars did.

‘It’s yet another piece of evidence which makes it more likely life came to Earth on a Martian meteorite, rather than starting on this planet.’

All living things are made from organic matter, but simply adding energy to organic molecules will not create life.

Instead, left to themselves, organic molecules become something more like tar or asphalt, said Professor Benner.

The minerals from Mars could have come to Earth via volcanic eruptions or meteorites (Picture: Nasa)

He added: ‘Certain elements seem able to control the propensity of organic materials to turn to tar, particularly boron and molybdenum, so we believe that minerals containing both were fundamental to life first starting.

‘Analysis of a Martian meteorite recently showed that there was boron on Mars – we now believe that the oxidised form of molybdenum was there too.’

Another reason why life would have struggled to start on Earth was that it was likely to have been covered by water, said Professor Benner.

Water would have prevented sufficient concentrations of boron forming and is corrosive to RNA, a DNA cousin believed to be the first genetic molecule to appear.

Although its is believed there was water on early Mars, it covered much less of the planet.

‘The evidence seems to be building that we are actually all Martians – that life started on Mars and came to Earth on a rock,’ said Professor Benner, speaking at the Goldschmidt 2013 conference in Florence, Italy.

‘It’s lucky that we ended up here nevertheless, as certainly Earth has been the better of the two planets for sustaining life.

‘If our hypothetical Martian ancestors had remained on Mars, there might not have been a story to tell.’

Nasa

美科學家︰我們都是「火星人」

自由時報 – 2013年8月30日 上午6:16

火星隕石 攜生命物質撞地球

〔國際新聞中心／綜合報導〕美國地球化學家提出證據指出，地球的「生命種子」可能並非土生土長，而是透過隕石或火山爆發，從「紅色星球」火星遠道而來。換言之，地球可能不只有火星來的「外星人」，地球所有生命其實都來自火星，因此我們都是「火星人」。

維斯海默科技學院（Westheimer Institute for Science and Technology）教授貝納（Steven Benner），是在美國地球科學學會和歐洲地球科學協會於義大利舉辦的歌德施密特大會（Goldschmidt Conference）上發表提出兩個論點，證明地球的生命來自火星。

貝納將論據之一稱為「瀝青」弔詭。他說，所有生物都是由有機物組合而成，但如果只是將熱與光等能量加到有機分子上，然後任由其自生自滅，它們永遠都 不會形成生命，而是會變成一坨「瀝青」狀的東西；但某些化學元素似乎可控制有機物變成「瀝青」的傾向，特別是硼與鉬乃攸關有機物形成生命的關鍵，因此擁有 這兩種元素的礦物質，對啟動生命至關重要。

配合地球環境 啟動生命

貝納指出，含硼的礦物質可幫助碳水化合物形成生命發生前的化學物質；鉬可擷取那種分子，重新組合後形成核糖，進而形成核糖核酸。最近的火星隕石分析發現火星有硼，貝納認為，火星上也有氧化形式的鉬。

貝納表示，鉬扮演的是催化劑，可讓有機分子發展成初期的生命結構，且鉬必須是高度氧化形式，才能影響生命的形成。由於地球初生時幾乎沒有氧氣，不可能擁有氧化鉬，因此地球生命起源並非原生，而是來自外部，極有可能是透過隕石撞擊或火山爆發來到地球，播下生命的種子。

貝納提出的第二個弔詭是「水」。地球初生時全部覆蓋在水面之下，不止硼結晶無法形成，一級遺傳分子「核糖核酸」（RNA）也會遭腐蝕；相較之下，火星雖然也有水，但覆蓋面積比地球少很多。

貝納說，前述兩種證據都建構了我們其實是火星人的理論。換言之，生命種子搭岩石便車，千里迢迢來到較適合成長茁壯的地球。

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