Interesting two questions. I am not aware that consensus science shows Mars ever had life but reports from the past certainly seem to show this. Originally published in July 1907, “If vegetation exists on Mars, as Prof. Lowell would have us believe, the existence of a flora is ground for suspecting a fauna. On Mars we find ourselves confronted in the canals and oases by precisely the appearance which the planet should show if it is an inhabited world. Dearth of water is the key to the character of the canals. The only available water on Mars is that coming from the semi-annual melting at the one or the other cap of snow. If there are intelligent beings on Mars, they must find some means of conducting the scant supply of water from the poles to the centers of populations.” —Scientific American, July 1907 More gems from Scientific American’s first 175 years can be found on our shiny anniversary page."
Here is another life on Mars report from 1943. Originally published in July 1943 “If, as appears to be probable, vegetation exists on Mars, life has developed on two out of the three planets in our system where it has any chance to do so. With this as a guide, it appears now to be probable that the whole number of inhabited worlds within the Galaxy is considerable. To think of thousands, or even more, now appears far more reasonable than to suppose that our planet alone is the abode of life and reason. What the forms of life might be on these many worlds is a question before which even the most speculative mind may quail. Imagination, in the absence of more knowledge of the nature of life than we now possess, is unequal to the task. There is no reason, however, against supposing that, under favorable conditions, organisms may have evolved which equal or surpass man in reason and knowledge of Nature. And, let us hope, in harmony among themselves!”
—Scientific American, July 1943
There is no evidence that life of any kind ever existed on Mars. Actually, there is no reason to believe there ever was life on Mars. The conditions that supported abiogenesis on Earth do not appear to have occurred on Mars. Of course there are those who believe Richard Hoagland and his ranting regarding the Cydonia Mesa. There are others who point out what appear to be “artificial’ structures on Mars, ignoring similar or even more artificial looking structures on Earth that have been proven to be natural.
Bottom line, there is no evidence of life on Mars, past or present.
Going back to the beginning usually helps.
Comment: why did life end on mars? when would it re-begin ...
This presumes that it did start and asks why it ended.
No answer possible. It may have existed. No evidence.
When would it re-begin?
Cannot re-begin if never started.
Not much more to be said.
The Northern Hemisphere of Mars is a flood basalt that is around 200 million years old by crater counting. Several Martian basalt meteorites have an age of about 180 million years.
There are sedimentary layers laid down by water that are several kilometers thick visible on satellite images.
There are several groups of asteroids having considerable inclination to the planetary plane including Pallas which could be the debris from a collision between Mars and an unknown object coming from below Mars.
The object entered Mars’ Southern hemisphere likely at Hellas Planitia. When the object exited it removed the equivalent of 4 to 6 kilometers from the Northern Hemisphere. The northern hemisphere has about 4-6 kilometers less radius. The residual heat of impact melted the debris resurfacing the surface of Mars and resetting the crater counting clock about 200 million years ago.
After the Viking landings NASA has not sent any chemical testing apparatus or any microscopes capable of detecting life (fossil or otherwise). The Viking landings had chemical tests which read positive for life. Later NASA said blah blah blah caused a chemical reaction which caused a false positive. The designer of the test refuted NASA’s analysis.
The US Geological Survey apparently has the final say on the ages of rocks on other planets. The USGS canon says that Mars has been in a time warp and everything about it is billions of years old without any exceptions.
Steam has been seen exiting from one of Mars’ volcanoes with NASA and the New York Times saying the steam was actually UFO’s.
Ignoring the USGS’s and NASA’s inexplicable derangement it is possible that microbial life is still present on Mars. Higher forms of life could have been present up to 180-200 million years ago before Mars’ atmosphere was blown away by a collision. They might have left some kind of fossils or biological chemical signatures as the dunes covered them.
Judging from how squirrelly NASA is acting I would say Yes there is life on Mars.
A volcano venting steam on Earth would not generate any controversy while the same event on Mars has NASA and the New York Times scrambling?
I think it has to do with the previously accepted (now in dispute) ages of flood basalts on Mars and the Moon. Those ages were produced by Houston.
The article that the picture of steam came from conceded that the Martian volcano was less than 200 million years old, by extension the entire region of Martian flood basalts is near the same age.
Crater counting of the Martian basalts gives an age of about 200 million years.
Crater counting of the Nearside flood basalts (Mare or Seas) on the Moon gave an age of around 300 million years (Eugene Shoemaker and others).
This is where my logic obviously goes off the rails. The Apollo program directly sampled those flood basalts on the Moon. According to Houston none of the samples were less than a billion years old and the average was over three billion years old.
So, my eyes are lying and NASA/Houston is telling the truth.
If the crater counting is correct (straight forward linear logic) then something catastrophic happened to Mars about 200 million years ago. Such a catastrophic event could have easily blown away Mars’ atmosphere. Therefore, that date is critical to understanding how long Mars could have sustained life.
Instead of some ancient date mumbled about solar radiation stripping the atmosphere we have a concrete date. Look at what solar stripping did to Venus’ atmosphere whose pressures and temperatures could slag a submarine. The higher gravity of Venus is more than offset by the higher temperatures and higher levels of solar radiation. Solar stripping is a single mosquito sucking all the blood out of an elephant.
This date allows Mars to have several billion years as a wet world with a substantial atmosphere. That raises the chances of microbial life to a near certainty.
There has been various proofs of water and an atmosphere suitable for life on Mars. There had been life on Mars at least a billion years ago if not thousands of years ago. Maybe, there are still some microorganisms left in frozen dry ice in the south pole and the north pole of Mars, waiting to be found by someone.
By the way, if a human goes to Mars, there would be life on Mars again, lol. And, I disagree with Mental Avenger. There are more evidences to believe that there was life in the past in Mars than the opposite.
But, if there hadn't been any life on Mars in the past, I don't think that there would be any life on Mars in the future. It seems that there has been a huge meteorite strike at the Equator of the Red Planet and most probably most of the craters around the Equator has been caused by the debris of that Meteorite. The Hellas Planitia was formed by that strike. Most probably, it was a small protoplanet which was ejected from the asteroid belt between Mars and Jupiter. And, the Phobos and the Demos might have been created by that strike. That may be the reason behind such low orbit of Phobos, it is the lowest orbit of any satellite of any planet ever found. That strike might have wiped out the atmosphere of the Red Planet and had turned it red. And, a whole new layer of soil might have been created by that huge meteorite and turned the whole of the crust of Mars rusty. I believe that if a rover digs deep inside the surface of Mars, it might find the original surface of Mars which might have been roasted by the asteroid.
And, the magnetosphere (and life) of Mars might have been wiped out by this catastrophe. This catastrophe had a huge shock effect which was felt across each and every atom of Mars, even at the core of it which wiped out the Magnetic Field of Mars. (No Magnetosphere = No Life)
But (yes, there is still a "but"), if life could survive on Earth even after that huge meteorite strike on Earth about 65.5 million years ago, then it might be possible that the microorganisms of Mars might have adapted to its surroundings. It might be true that some microorganisms still exist on the South and North poles of Mars, where there is dry ice (and, who knows if there is ice there or not).
Always remember: Life might have a beginning but it has no end.
"There has (have) been various proofs of water and an atmosphere suitable for life on Mars"There is a very large gap between these two statements. There is a very great difference between Prokaryotic cells and even the least advanced mammals. "There had been life on Mars at least a billion years ago if not thousands of years ago."
Can you point me to any evidence of even the simplest form of life on Mars? You say there had been life there. What is your evidence?
I think you all are looking past the evidence that there are canyons on Mars, and canyons can form only by a river. And, we all know that life was created on Earth due to abiogenesis. So, by putting that logic it is possible that there were microorganisms on Mars and maybe there is it still on Mars because life finds a way to survive. Wikipedia also says that there might have been life-supporting elements on Mars. And Cat, maybe pigs don't fly but if you were sent back 300 million years ago, would you guarantee that there would be a species called Homo Sapiens roaming around Earth after 300 million years ago?
This picture shows both the canyons and the northern lava field. The oval block at the left appears to be a large fracture block. The impact body hits at Hellas Planitia on the lower right and exits somewhere to the north. It appears that the path did not go through the center of Mars but off to one side.
I suggest that those canyons are fractures on a planetary scale.
The “alleged” northern ocean of Mars never existed. Oceans form after a planet has coalesced into a sphere. 4-6 kilometers is missing from the northern hemisphere after an object passed through Mars. The canyons were fractures that did not connect to the main body of molten rock. The molten rock did fill in the fractures of the northern hemisphere.
The fracture/canyons likely occurred at the same time as the collision.
Yes, you are seeing some evidence of water flowing in those canyons but if it was excavated by water where did the sediments go? Where is the upstream and the downstream?
"I think you all are looking past the evidence that there are canyons on Mars, and canyons can form only by a river. And, we all know that life was created on Earth due to abiogenesis. So, by putting that logic it is possible that there were microorganisms on Mars"
Please explain what you mean by "that logic". I cannot see any logical causal evidence of the presence of water and the development of life. Water does not cause life.
From what we know of life (which is a great deal), there is a narrow range of requirements for its origin (abiogenesis), and long term survival. If there ever was life on Mars, it would likely be found well below the surface, where it might have arose in ancient oceans. If you want to really look for past life on Mars, you will need to do some serious excavations, and likely deep.
And Cat, pigs will never evolve into flight. Too many people eat pork, and don't want their food flying off, much less dumping on them (see Animals by Pink Floyd - that flying pig on the cover is only a blimp ). If "pigs" ever did evolve flight, they would be so far down the evolutionary line they wouldn't be pigs anymore.
Just like therapods evolving flight. No chance. These things won't/didn't happen no matter how much anyone wants them to.
These are reasonable arguments. As noted in an earlier post, life likely arose (if at all) in a salty ocean like on earth, and that might limit atmospheric requirements, at least to some extent. As long as the water is not being driven off by excess radiation, etc., it would likely persist long enough for life to evolve.
One should consider that fossils of life on earth date back to at least 3.7 bya, as shown in stromolites, which still exist today. Stromolites of that age suggest that life arose on earth much earlier.
The conditions on earth ca. 4 bya would help to consider the start-time for life arising on Mars. It might be at or nearly the same time!
The next question : what would be life's time frame before becoming totally extinct, assuming there are not oceans teaming with life under Mars surface.
Out of curiosity, why would you put 200 mya as a closure time for abiogenesis on Mars? Surely it could be much earlier, just wondering about that time frame.
Life could have arisen earlier but the collision event at about 200 million years ago might have made it more difficult afterwards. It is possible that the massive volcanic activity after the event might have opened up new environments and niches. The loss of atmosphere might have been balanced out by higher underground temperatures.
Reviewing some of your posts, I have trouble believing that an impactor at Hellas Planitia would carry through the planet and exit at the opposite side of its entry. Mars seems much too large for such an event. Some would think that most of the impactor's mass would be deeply buried under the crater, or ejected back into space.
If the impact at Hellas Planitia actually caused the floods in the northern hemisphere, it would seem to me more likely to result from a large shock wave with its force-apex directed at the center of the flood plane, in-line with the impactor's "direction". This is a very interesting observation I was unaware of. If memory serves me correctly, four of the major volcanic forms on Mars have antipodal impact craters to account for them. Is that correct?
Also, I remember seeing images of large, block-like objects that appear as ancient ice sheets which have broken apart and moved away from each other, and then fixed in place. They appear almost like a jig-saw puzzle where you can see how they fit together at one time. It is postulated that these resulted from an ancient ice "cap" over an ocean of water, and now covered up after many millions of years of "debris overage". Are you familiar with these objects? I have never seemed to find these images again in a search.