Now that we can image Mars’ surface to a very high degree (enough to spot landers and rovers), has the existence of visible life on Mars’ surface been completely ruled out? No patches of ultra-hardy lichen, no tracks left by movement, no animals that look like rocks, etc.? Or have we examined too little of Mars’ surface to rule out very rare instances of surface life?
No. Life, if it exists/existed on Mars, might never have been more than microscopic. We certainly haven’t looked hard and wide enough to rule that out yet.
No, because to my knowledge not every square mile (or square kilometer for Dopers outside the US) has been surveyed from space or on the ground. That means that there are vast areas of Mars which have not been searched.
There’s also the possibility that life exists underground on Mars. There have been no surveys of the myriad canyons, caves or underground chambers so there could easily be life in those places. WHen/if Man ever travels to Mars we could potentially eliminate life in those places.
Finally, there may be forms of life (silicon-based for example) with which human beings are unfamiliar on the planet. Since we are searching for life that resembles what we know, we may miss life that we have never seen here on Earth.
“WHen/if Man ever travels to Mars we could potentially eliminate life in those places.”
( Quote function is not working for me…:mad: )
That’s probably what we’d do!
I think that we should really be focusing on sailors fighting in the dance halls.
Are they on to me yet?
I’d say the chances are a million to one.
Just don’t say that to the girl with the mousy hair.
I’m whooshed… reference?
David Bowie, Life on Mars.
(one of my favorite songs, btw)
Null hypothesis: there is no life on Mars.
As of right now, the null hypothesis has not been rejected.
This does not mean there is no life on Mars. It simply means that, if there is life on Mars, we have not yet detected it.
The HiRISE instrument on the Mars Reconnaissance Orbiter has imaged a pretty sizeable minority of the Martian surface with ~1 foot resolution. It gave us some spectacular images of the Curiosity rover as it descended and after landing.
The MRO also has a lower resolution, wide-angle camera with a 6-meter resolution. It mapped half of the martian surface between 2006 and 2010, so I imagine we have a nearly complete map by now.
So, there’s robotic life on Mars, then.
Can’t prove a negative. But we can say with great certainty that there is no evidence of any sort of multicellular life, and certainly no megafauna. Bacteria and other microorganisms? Maybe somewhere.
Not sure what you mean by “overt.” Perhaps an example of a “covert” life form would be helpful.
It is somewhat tiresome to watch TV and movies that depict aliens living in a total vaccuum with no apparent food sources or environment to sustain them.
Heffalumps and Woozles.
Simply put, if there was life on Mars, it would be detectable everywhere on Mars.
Null hypothesis: there is life on Mars.
As of right now, the null hypothesis has been rejected.
Probably, but not necessarily. You could hypothesize life evolving back in the days of liquid water, and then finding itself confined to a few niches as the climate changed. Someone suggested cave life upthread, for instance.
To quote Timothy Ferris, “Absence of Evidence is not Evidence of Absence”.
That said, while I find it highly likely that somewhere in the millions of galaxies we will never reach that there is intelligent and certainly non intelligent life, I am convinced there is and has never been life outside of Earth in our Solar System.
One way to look at things: Could we detect life on Earth solely through remote observations, a few orbiting satellites, and a handful of landers? Certainly we could easily detect cities, forests, algal blooms, and other large scale ecosystems. We could probably even detect large herds of megafauna from orbital images, and smaller plants and critters with the rovers. But we probably would miss microbial life in more barren regions.
For example, the Atacama Desert is one of the most barren places on Earth, but it is teeming with microbial life. Even in the “hyperarid” regions of the desert, there are thriving communities of microbes. Importantly, the same sorts of experiments used on Mars landers do not detect signs of life in the “hyperarid” soils of the Atacama.
To sum up, we could have easily detected megafauna, big ecosystems, or conditions comparable to the less hostile deserts on Earth. If there is any life on Mars, it is either microbial, very rare, or based on a chemistry that is radically different from anything on earth.
Really? Considering the billions of years of exchanging material between planets and moons through impacts and ejecta, and considering that many single-celled lifeforms and even a few multicellular lifeforms have shown some ability to survive in a stasis-like state in a vacuum and under high radiation, I think it’s quite likely that, today and/or in the past, places like Mars and various moons of Jupiter and Saturn have hosted lifeforms similar to Earth-life.