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18

There are two convincing papers (1,2) arguing that the observed "nanobacteria" are in fact mineral/protein complexes and not any living organisms. In (1) Martel and Young created very similar looking particles from calcium carbonate in vitro. The calcium carbonate precipitations can even look similar to dividing cells: After 5 days of serum incubation, ...


13

I like your question! Low surface pressure on Mars (averaging 600 Pa or about 1/170 of Earth's at sea level) is only one difficulty that an organism would have to contend with. In addition, mean surface temperatures are ~210 K (-63 C), the surface ultraviolet flux is extremely high (no ozone layer) and an aridity comparable to the Atacama desert. On the ...


12

I did some research on the topic and came accross this paper by Johnson et al. I am not a zoologist, so everything I write here is taken from the references paper. The authors used genetics to estimate gene flow between different populations of limpets Lepetodrilus fucensis which is considered to be an endemic hydrothermal vent animal. They used a ...


10

Following up on Alexander's response, I read a little more on the subject by looking at some of the references in the Johnson et al. paper. This paper discusses an interesting case where researchers could study a hydrothermal vent ecology before and after a catastrophic eruption giving a "natural clearance" experiment. Since endemic organisms were ...


10

Background There are basically three highest taxonomic levels: bacteria, archaea and eukaryotes. Many sources distinguish only prokaryotes and eukaryotes, subdividing prokaryotes into bacteria and archaea. Other sources posit archaea as a third domain on the highest level. That's a long debate though and fortunately not the topic here. By appearance, the ...


6

OK, so we know a couple of things about life in the universe. Note, however, that this is not really an answer and is also not very biological in nature. So, we don't know how life began on the Earth. However, do know that: (1) The probability of life evolving on a planet in the universe is non-zero (since we exist) and, (2) So far, we have not found ...


5

It is interesting to note that, in the Wikipedia article, it states that The amino acids were racemic (that is, the chirality of their enantiomers are equally left- and right-handed), indicating that they are not present due to terrestrial contamination". This implies that, if a 'life form' did create these proteins, they are fundamentally quite ...


5

Curiosity is on the Martian surface and is equipped with a slew of laboratory equipment. But not, incidentally, equipment to detect life. What would Curiosity need to discover to prove there is or has been life on Mars? Would it have to find DNA …? No. In fact, DNA would be lousy evidence of life on Mars, it would almost certainly be a ...


4

Answer to your title: ex•tra•ter•res•tri•al [ek-struh-tuh-res-tree-uhl] adjective outside, or originating outside, the limits of the earth Answer to your post: There is a whole field of study revolving around these questions called astrobiology. It is assumed that extraterrestrial life forms will have some sort of information storage similar to DNA ...


4

I think it's fair to say that we don't really know how these more complex organic molecules formed abiotically, but we can say that carbonaceous chondrites - a class of carbon and organic molecule bearing meteorites to which Murchison belongs (specifically CM2) - have experienced at least three distinct chemical histories: In the interstellar medium (ISM) ...


4

This is not a definitive answer. The solvent closest to water in its properties such as dielectric constant, melting/boiling points, etc are formamide and sulphuric acid. F S W Melting point (⁰C) 2 10 0 Boiling point (⁰C) 210 337 100 Dielectric Const 109 84–100 80 Specific ...


3

According to this, 1.2% of stars have planets that can support life. According to Google, there are 300,000,000,000 stars in the Milky Way. That means 3,600,000 stars can support life. Each of these stars is estimated to have 1-2 planets that can support life. For the sake of simplicity, I'll use 1.5 to represent this, since it is the average of 1 and 2. ...


3

I wouldn't say that there is an established protocol - claims of alien life are not commonly testable or even legitimate - but if something were discovered and deemed "alive," a fairly good sign it was alien would be if its genetic makeup were based on something other than DNA or RNA. That would be a dead giveaway the organism had side-stepped every known ...


3

Yes we should be and we are! Scientists have been analysing cometary material - but its a challenging task. The problem with looking at meteoritic material from comets on Earth is that it is generally contaminated with material from Earth. In addition, meteorites get physically altered during their passage through the Earth's atmosphere due to the high ...


2

In the simplest sense, extraterrestrial life is life found beyond the Earth. Defining what life itself is notoriously difficult - perhaps the best is a system which is subject to Darwinian evolution? However, the term "extraterrestrial life" does not necessarily imply that said life (if found) originated in situ. For example, if we do find (presumably ...


1

We might imagine living things that are very different from what we know. There is no conceptual reason for limiting life in its relation to water for example. Moreover, the definition of what is alive is really unclear. We classified more or less arbitrarily objects we know on earth as being living or not living but this does not give any clear definition ...


1

This is a cool idea and definitely we have found a lot of the chemicals important to life are associated with comets which have a lot of water too. Another issue besides the v. low temperatures on comets, when they warm up to the sun are not long lived so I wonder if the a shorter lifespan would be an issue when they are seen in the temperate zones of the ...



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