生物谷綜合：眾所周知，地球上已發(fā)現(xiàn)的生命都是有機(jī)的,，那么,，宇宙中所有的生命都是有機(jī)的嗎？現(xiàn)在誰(shuí)也無(wú)法回答,。不過(guò)，一個(gè)國(guó)際科學(xué)家小組的最新研究表明,，星際塵埃中的無(wú)機(jī)物質(zhì)有可能形成一種類(lèi)似生命基礎(chǔ)的螺旋結(jié)構(gòu),。這一發(fā)現(xiàn)暗示著地球之外的生命或許并不需要有機(jī)分子作為基本材料，同時(shí)也為地球上生命起源提出了一種新的可能的解釋,。相關(guān)論文發(fā)表在8月9日的《新物理學(xué)雜志》（New Journal of Physics）上,。
這聽(tīng)起來(lái)確實(shí)有些天方夜譚。不過(guò),，俄羅斯科學(xué)院普通物理研究所（General Physics Institute）的V.N. Tsytovich和德國(guó)馬普地外物理研究所（Max-Planck Institute for Extraterrestrial Physics）以及澳大利亞悉尼大學(xué)的科學(xué)家通過(guò)研究等離子體中的復(fù)雜的無(wú)機(jī)原料混合物發(fā)現(xiàn),，只要有合適的條件，無(wú)機(jī)粒子能夠變成有組織的螺旋結(jié)構(gòu),。而且,，這些螺旋結(jié)構(gòu)之間會(huì)以與有機(jī)物質(zhì)和生命相關(guān)聯(lián)的方式發(fā)生相互作用。
到目前為止,，物理學(xué)家認(rèn)為,，等離子體中的粒子之間幾乎沒(méi)有組織性可言。不過(guò),，Tsytovich和同事利用分子動(dòng)力學(xué)計(jì)算機(jī)模型證明,，隨著電荷逐漸分離和等離子體變得極化，上述的自組裝過(guò)程是有可能發(fā)生的,。研究人員認(rèn)為,，這些由固體粒子所形成的螺旋結(jié)構(gòu)自身都帶有電荷，因而彼此間會(huì)相互吸引,。
更不可思議的是,，研究人員表示，這些螺旋結(jié)構(gòu)還會(huì)經(jīng)歷一些通常與生物分子（如DNA和蛋白質(zhì)）相關(guān)的變化,。比如,，這些螺旋結(jié)構(gòu)會(huì)斷開(kāi)、分叉,，進(jìn)而形成兩個(gè)原始結(jié)構(gòu)的副本,。此外，這些螺旋結(jié)構(gòu)間的相互作用還會(huì)促使它們中的不穩(wěn)定結(jié)構(gòu)分解,，進(jìn)化成更多的穩(wěn)定結(jié)構(gòu)留存于等離子體中,。
Tsytovich說(shuō),，“這些復(fù)雜的等離子體結(jié)構(gòu)所表現(xiàn)出的自治、復(fù)制和進(jìn)化的性質(zhì),，使它們滿(mǎn)足了一種無(wú)機(jī)生命候選物質(zhì)的所有必需條件,。”
研究人員表示，形成螺旋結(jié)構(gòu)等離子體條件在外太空廣泛存在,。即使是在地球上,，雷擊也會(huì)產(chǎn)生等離子體。因此,，有可能原始地球上最先出現(xiàn)的是無(wú)機(jī)生命形式,，而有機(jī)分子以它們作為模板，演化成為今天的樣子,。（科學(xué)網(wǎng) 任霄鵬/編譯）
原始出處:
New Journal of Physics
Collision-dominated dust sheaths and voids - observations in micro-gravity experiments and numerical investigation of the force balance relations
V N Tsytovich et al 2003 New J. Phys. 5 66 doi:10.1088/1367-2630/5/1/366
V N Tsytovich1, G Morfill2, U Konopka2 and H Thomas2
1 General Physics Institute, Russian Academy of Science Moscow, Vavilova Street 38, 117942, Moscow, Russia
2 Max-Planck Institute fur Extraterrestrische Physik, 85740 Garching, Postfach 1603, Germany
E-mail: [email protected], [email protected], [email protected], [email protected] and [email protected]
Part of Focus on Complex (Dusty) Plasmas
Abstract. Numerical solutions of stationary force balance equations are used to investigate the possible dust configurations (dust structures) in complex plasmas between two floating potential plane electrodes. The distance between electrodes is assumed to be larger than the ion-neutral mean free path and the hydrodynamic description is used. It includes the known forces operating in this limit, the ionization source and the dust charge variations. The stationary balance equations are solved both in the case of the presence of one-size dust grains and for the case of a mixture of grains with two different sizes. Recent micro-gravity experiments with single-size dust grains and two-different-size dust grains show the formation of a system of dust sheaths and dust voids between the two plane electrodes. The observed configurations of dust structures depend strongly on the gas pressure and the degree of ionization used. The numerical investigations are able to show the necessary conditions for the types of structure to be created and give their size. The size of the structures observed is larger than the ion-neutral mean free path and is of the order of magnitude of that obtained numerically. The numerical investigations give details of the spatial distributions, the dust particles, the electron/ion densities, the ion drift velocity and dust charges inside and outside different dust structures. These details have not yet been investigated experimentally and can indicate directions for further experimental work to be performed. The single-dust-sheath structure with single-size dust particles surrounded by dust free regions (dust wall-voids) and floating potential electrodes is computed. Such a structure was observed recently and the computational results are in agreement with observations. It is shown that more often a dust void in the centre is observed. It is found that a dust void in the centre region between two electrodes is formed if the ionization rate is larger than the critical ionization rate and that in the presence of the floating potential walls the central void should be surrounded by two dust sheaths. The necessary condition for this dust structure to be formed is found to be that between the sheaths and the walls there are formed two other wall-void regions. The size of the central void and the distributions of the structure parameters in the two sheaths and in the three voids are computed. The qualitative features of the structure obtained in the numerical computations correspond to those observed. The distributions of the structure parameters in the case of the two dust sheaths are quite different from that for the case of a single central sheath. The possible structures between the electrodes for the case of the presence of dust particles of two different sizes are analysed numerically. It is shown that dust particles with different sizes cannot coexist in equilibrium at the same position and that the regions with different size dust particles must be separated in space. This conclusion is in agreement with most observations performed so far. It is illustrated numerically that for the case where the central void is present the dust particles of larger size form a separate dust sheath which should be located at larger distances from the centre than that for the smaller dust particles. This result also coincides qualitatively with the observations. Computations for the distributions of the parameters in the larger size dust sheath were performed both in the case where the central part is occupied by a dust sheath with smaller size dust particles and for the case where in the central part there exists a dust void surrounded by dust sheaths with smaller size dust particles. The size of the dust void between the sheaths with different size dust particles is calculated and shown to be small as compared to the sheath thickness. In the sheath with larger size dust particles the distribution of dust and plasma parameters differs qualitatively from that of the first dust sheath with smaller size dust particles. The stability of the stationary structures both with respect to excitation of dust convection cells and with respect to oscillations of dust void size is discussed.
Received 20 January 2003
Published 9 June 2003
