why do they always say that if there is no water on a planet or there isn`t oxygen there can be no life in it?

Question

why do they always say that if there is no water on a planet or there isn`t oxygen there can be no life in it?, i have heard there is an animal, almost microscopic that can live in extremly hi temperatures so if it does there will be no water because the heat wiould evaporate it, and what if something would need helio or nitrogyn insted of oxigen?

Answer 1

When they say "no life," they are saying "no life as we know it."
While there are theoretical lifeforms that do not require liquid water, we have never come across them. Even those hi-temp critters are living IN water (near the "black smokers" volcanic vents on the ocean floor).
So to find something we would immediately recognize as "life" requires water in its liquid form at least part of the time. Also, oxygen is the major reactive chemical Earth life requires. No oxygen means that the entire chemistry of the alien lifecycle would be different.
When you are trying to deduce the existence of a thing from trillions of miles away, you look for the familiar, not the unknown.
So, yeah, there may be smart rocks, helium III coldlife, intelligent gas clouds (not "gasbags" - we have those in government here on Earth), or something totally un-imagined.
But for the purposes of telescopic searching, we are looking for Earth-like life.

Answer 2

Really high temperatures doesn't necessarily mean no water, only that it may not be in liquid form. I think they base this on that all life that we know of needs water and oxygen to survive. If we are going to imagine life existing other places, the easiest thing is to imagine that it would exist as life does here. I don't think that too many people have completely written off the possibility of life outside our world existing by some means other than water, and oxygen it just doesn't seem a high probability.

Answer 3

Or why do they try to tell you the make up of planets far beyond and then mars the closest one they have to send robots there to confirm their ideas
i mean, if they can not be sure about mars then they really should not try to give answers for pluto

oh, i hogged that question with another question
my bad

yeah, good point
I don't know if they definitely say that but I get the same feeling they do
That's true if they assume all life has to exist the way we all do
why not have some off the wall life that lives off light and sulfuric gas
Definitely never thought about that because they do usually say "nasa scientist find far off planets that could support life"
seems they assume life needs earth elements
why not alternative life with alternative elements

Answer 4

What "they" are talking about is life as we understand and know it, like life forms on Earth. Oxygen isn't by any means a requirement for life to begin. In fact when life first formed on Earth billions of years ago the atmosphere was almost totally without oxygen. Water is thought to be a basic requirement because our science thinks that water is needed as a kind of mixing agent or solvent for the various chemicals from which life can grow.

As you point out there can be conditions completely lacking any of what we consider to be requirements for life to begin, and yet life has started anyway.

Answer 5

"they" haven't studied science, that's why...

Life evolved on earth before earth had oxygen in its atmosphere. This theory is based on the laws of chemical thermodynamics. The law states that pure Oxygen will freely combine with other elements and will not remain pure indefinetly. The reason the earth has pure oxygen in its atmosphere is the fact green plants produce this gas. This replaces the free oxygen in the atmosphere which is used by animals who combine it with carbon to form carbon dioxide.

Before the earth had oxygen, it was covered with microscopic organisms which did not require oxygen to survive. These bacteria are known as anaerobic and many species still exist. They must live deep underground because oxygen is poisionous to them. Some also live in sewers and there are many of them in the intestine. Yeast isn't a bacteria but it too can live without oxygen. This fungus can tolerate oxygen, but can also live without it.

The earth was not always covered in liquid water, but water was present when life evolved, and this is why life is almost always associated with liquid water. Water is a polar compound and this molecular polarity is exploited by the chemistry of life. However, there are other molecules which are also polar. Ammonia is such a substance. Liquid ammonia does not naturally exist on earth because its boiling point is about a hundred degrees below zero. There are places in the solar system which probably have liquid ammonia however. It might be possible that there is "life" whose chemistry is based on ammonia instead of water. These creatures would live at temperatures where water would be solid, as well as carbon dioxide. Methane and ammonia would be liquid.

Saturn's moon titan is now known to have lakes and rivers which are filled with liquid methane. The viking mission to Mars tested the soil for life but used water. It is possible that Martian life may be based on hydrogen peroxide. Water is H2O and hydrogen peroxide is H2O2. The difference is that peroxide is liquid long after water has frozen. The average temperature on Mars is about 30 degrees below zero.

Perhaps the first "alieans" we meet will appear to be metallic robots because the life froms inside them are ammonia based creatures living in a space suit. Should the suit rupture, humans might think these creatures were actually composed of a foul smelling gas, for the poor creature would vaporize immediately on earth's surface. However, humans might visit a planet like venus whose average temperature is 800 degrees and whose atmosphere is saturated in battery acid. Should the suit rupture this time, flames would shoot out.These alieans would get the impression humans were composed of fire.

Answer 6

Well there are animals that can live in extremely high temperatures. But this is also under extreme pressure, like at the bottom of the oceans near the thermal vents. The temps there are hot enough to melt lead but at such pressure the water can't boil.

As far as life as we know it, there needs to be water but not oxygen, many kinds of bacteria can life with out oxygen, but we know of know organisms that can survive without water.

Answer 7

All life on Earth needs water. There are no exceptions. Some microbes may be able to live on a small amount of water, and some may be able to make spoors or seeds or whatever that can survive without any water, but with no water at all no microbes could live to make spoors or seeds. However, oxygen is not required. There are microbes on Earth that live without oxygen. In fact they are killed by oxygen. Clostridium botulinum (that causes botulism) is one.

Answer 8

It is very possible that life somewhere else was able to develop based on other elements and molecules. But for all we know, life is based on water. So looking for water is a good start to finding other life.

Answer 9

Neptune...why pass digging right into a deep gravity nicely which includes that. One could in basic terms ought to divert a set of comets to get the H2O and organics and then a set of asteroids to help strengthen the mass somewhat..take all those ones that are Earth-crossers and deliver them to Mars fairly. you does no longer desire an excellent deliver the two; in basic terms use the two mass-drivers or image voltaic sails to divert those comets or asteroids. area mirrors ought to be used to heat the planet's floor to make it liveable.

Answer 10

Since we haven't gone beyond our own solar system,Earth
is our only frame of reference at the moment. You're right,
there could be forms of life out there with much different needs. Maybe some day our descendants will find out.