So What if We Found Evidence of Past or Current Life on Mars?

[HappyMartian]

An Astrobiological View on Sustainable Life By Takeshi Naganuma
At: www.mdpi.com/2071-1050/1/4/827/pdf

"The sources of external dissociation energy are the Sun (solar radiation) and the Earth (geothermal heat including 40K radioactivity); and water molecules split via the light reaction of photosynthesis, photochemical reactions (photolysis), 40K -radiation (radiolysis) and the high-temperature water-rock interaction (thermolysis) (Figure 7)."

And, "It is interesting that methane (CH4) is present in the Martian atmosphere [16,17], and that volcanic activity as recent as four million years ago is suggested [18]. This being so, a modern biosphere may be sustained in the Martian subsurface that could store liquid water and remnant geothermal heat [19]. Another possibility is hydrogen (H2) production via hydration of one of the most ancient volcanic rock of the Earth, komatiites, whose occurrence on Mars is also suggested [20]."

And, "This is the splitting-of-water catalyzed by komatiites, and a recent experiment confirmed that the komatiite-catalyzed H2 production is robust enough to support H2-based methanogenesis [21]. Splitting-of-water catalyzed by komiites is likely to be a source of sustaining life forms on ancient Earth and Mars, and the possibility may extends to modern Mars."

And, "Both liquid water and volcanism are postulated to occur under the ice crust of Europa, Jupiter’s J2 satellite [22]. That is, geothermal split of water is likely to occur in Europa, as well as photochemical splitting of water in Europa’s thin atmosphere [23]."


Cheers!

[HappyMartian]

"According to Brown officials: 'First-time measurements of lunar melt inclusions show that some parts of the lunar mantle have as much water as the Earth's upper mantle. The results may change the prevailing theory about the Moon's origin as well as shed new light on the origin of water at the lunar poles.'"

And, "Based on the latest study, it's also believed that water-ice detected in craters at the lunar poles by several recent NASA missions may have come from historic volcanic eruptions rather than comet and meteor impacts. Also based on the study: More talk of construction on the moon. Location location location."
From: NASA Study Finds Even More Water on the Moon (100 Times More!)
At: http://www.treehugger.com/clean-technology/nasa-study-finds-even-more-water-on-the-moon-100-times-more.html



"Could microbial life exist inside Enceladus, where no sunlight reaches, photosynthesis is impossible and no oxygen is available? To answer that question, we need look no farther than our own planet to find examples of the types of exotic ecosystems that could make life possible on Saturn’s geyser moon. The answer appears to be, yes, it could be possible."
A Perspective on Life on Enceladus: A World of Possibilities  by Chris McKay and Dennis Matson
At: http://www.nasa.gov/mission_pages/cassini/media/enceladus-f20080326.html



"While Vesta is all dense rock and metal, Ceres appears to contain large amounts of ice. That could help solve another open question of the solar system: Where did Earth’s water come from?"

And, "It might have come from Ceres-like bodies that formed farther out in the solar system and then were pulled in by a migrating Jupiter, Dr. Walsh said."
From: Observations of an Asteroid Provide Hints of How the Earth Came Together 
At: http://www.nytimes.com/2012/05/11/science/space/asteroid-vesta-proves-to-be-dwarf-planet.html



"Furthermore, Ceres (1) is a differentiated body with a rocky core and an icy mantle, possibly still partly liquid, with a depth of more than 100 km; (2) may have or have had hydrothermal vents at its rocky core [5] and thus life may have evolved early; (3) has not been damaged much during the LHB, as it kept its icy mantle; (4) its impact ejecta need only a small Δv to transfer to Earth or Mars, and (5) is relatively accessible to further research."

And, "The seeding of the terrestrial planets from Ceres is a hypothesis that can be tested by, first, the detection of life in the crustal layers of Ceres, and secondly, a commonality of Cerean life with Terran and possible Martian and Venusian life. Third, spores of life from the Cerean ocean may be, or have been, ejected by icy volcanism. Fourth, biomarkers of Cerean life might be found in the ices at the Moon's poles and on the surface of other main belt asteroids, as there the arrival of ejecta from Ceres may have taken place at low velocity."
From: Glaciopanspermia: Seeding the Terrestrial Planets with Life?
At: http://sciwww.esac.esa.int/SB/MARSEXPLORATION/docs/Presentations/Houtkooper.pdf


See also: Life on Ceres: Could the Dwarf Planet be the Root of Panspermia?   At: http://www.universetoday.com/26587/life-on-ceres-could-the-dwarf-planet-be-the-root-of-panspermia/



If we find life or fossils on Mars, one likely consequence is that we will look carefully for life on other bodies such as the Moon, Enceladus, Europa, and Ceres.


Cheers! 

[HappyMartian]

So What if We Found Evidence of Past or Current Life on Mars?

There would be some cultural influences that would get stronger...

Aliens calling? Send in the robots!  By Alan Boyle
At: http://cosmiclog.msnbc.msn.com/_news/2012/06/07/12109770-aliens-calling-send-in-the-robots?lite
"Hand pointed out that NASA's Kepler mission has detected thousands of potential planets in just one little patch of sky. That leaves plenty of opportunities for finding life out there, and plenty of opportunities for life to make its way here."


And maybe all the Spaceship Earth's military folks would want to get real serious about international cooperation issues.

The Aliens Would Win  By Sue Karlin  June 06, 2012
At: http://spectrum.ieee.org/tech-talk/geek-life/hands-on/the-aliens-would-win
"Whoever takes the trouble to come visit us is probably a more aggressive personality. And if they have the technology to come here, the idea that we can take them on is like Napoleon taking on U.S. Air Force. We’re not going to be able to defend ourselves very well. But if I wanted that to be correct, it would be a very short movie."


And we would get a lot more serious about searching for ETs...

Stepping Up the Search for E.T.  By Sue Karlin  Tue, March 06, 2012
At: http://spectrum.ieee.org/tech-talk/geek-life/hands-on/stepping-up-the-search-for-ets
"The Search for Extraterrestrial Intelligence (SETI) Institute is back in business in a big way, teaming with the Science Channel and calling for thousands of citizen scientists to help SETI astronomers look for alien signals in real time."


Yep, it is a bit hard to imagine all the consequences. 

Cheers!


Edited.

[HappyMartian]

National Academy of Sciences: Microbial life could survive on Mars  Saturday, June 09, 2012
At: http://www.capitolcolumn.com/news/national-academy-of-sciences-microbial-life-could-survive-on-mars/
"A new DNA analysis of the Martian-like landscape on top of some South American volcanoes has found communities of bacteria, fungi, and archaea. These organisms are not just capable of surviving there, but also deriving their energy in ways not currently known."

Cheers!

[HappyMartian]

"At Gale you don't need to reconstruct the layers. You can see how they go from older to younger. You've got time's arrow always pointed in the right direction. It's all laid out very simply," Grotzinger said."

And, "'Let's assume life did evolve on Mars. Where are the places that have habitable environments and the highest preservation potential?' he said. 'If you do this as a random walk, you're doomed to failure because you only have so much time and the clock is ticking.'"

From: UPDATE 1-US robotic rover to seek Martian life with new focus  Mon Jun 11, 2012
At: http://www.reuters.com/article/2012/06/11/space-mars-idUSL1E8HB9K020120611

[HappyMartian]

"New research from US and Kiwi scientists analysing the sources of the gas methane could provide clues to the existence of life on Mars."

And, "The study, published this week in the journal PNAS, revealed that the amount of hydrogen included in methane gas can act as indicator of the presence of life."

And, "Dr Chris Oze, from the University of Canterbury, and colleagues ran several experiments to identify the differences between methane produced from living and non-living sources. The researchers were able to show that gas produced by the metamorphisis of rocks in in the Earth's crust has a higher methane to hydrogen ratio than gas produced by organisms such as bacteria."
Life on Mars? Check the methane
At: http://www.scoop.co.nz/stories/SC1206/S00026/smc-heads-up.htm



"The team of four, made up of research designer Dr Oze with researchers from Bryn Mawr College in Pennsylvania and the US Geological Survey, found that living things convert hydrogen into methane faster than geothermal processes, so in places where life exists there will be more methane than in places where there is no life."

And, "They found that where there was no life, the lowest ratio of hydrogen to methane was 42:1 (meaning 42 times as much hydrogen as methane), whereas when life was present the ratio of hydrogen to methane was maximum 33:1 and more often was 10:1.
From: Kiwis help in search for life on Mars
At: http://www.3news.co.nz/Kiwis-help-in-search-for-life-on-Mars/tabid/1160/articleID/257437/Default.aspx

[HappyMartian]

"Paradoxically, the find actually boosts prospects for finding signs of ancient life in Martian rocks. The carbon in MMC was originally chemically reduced – meaning it carries extra electrons and is quick to react. Such readily available and reactive carbon could have joined with other elements to create complex chemical molecules, perhaps even life."

And, "'The presence of organic carbon at or near the Martian surface provides a potential nutrient source for putative life,' says co-author Francis McCubbin."
From: Bottled carbon from Mars bodes well for ancient aliens  By MacGregor Campbell   May 24, 2012
At: http://www.newscientist.com/article/dn21847-bottled-carbon-from-mars-bodes-well-for-ancient-aliens.html




"They found that the amount of water in places of the Martian mantle is vastly larger than previous estimates and is similar to that of Earth's. The results not only affect what we know about the geologic history of Mars, but also have implications for how water got to the Martian surface. The data raise the possibility that Mars could have sustained life."

And, "McCubbin concluded, 'Not only does this study explain how Mars got its water, it provides a mechanism for hydrogen storage in all the terrestrial planets at the time of their formation.'"
From: Extensive water in Mars' interior     June 22, 2012
At: http://www.marsdaily.com/reports/Extensive_water_in_Mars_interior_999.html


Cheers!

[gospacex]

OK, before you all jump all over me, I’m playing Devil’s Advocate here.  Let’s assume that one of our robotic missions found evidence of fossilized past life or current life of some form. Now we are talking about some microbial or plant life for example, not gazelles springing across some savannah.  What exactly does that mean we are supposed to do? How would that change anything on how we are doing spaceflight on a program basis?

Expect shrill cries from eco-extremist crowd demanding that we never, never, never ever send humans to Mars. Not so much in the fear that astronauts could die (who cares, right?) but that evil imperialistic primates would mercilessly genocide peaceful oppressed Mars bacteria.

[HappyMartian]

OK, before you all jump all over me, I’m playing Devil’s Advocate here.  Let’s assume that one of our robotic missions found evidence of fossilized past life or current life of some form. Now we are talking about some microbial or plant life for example, not gazelles springing across some savannah.  What exactly does that mean we are supposed to do? How would that change anything on how we are doing spaceflight on a program basis?

Expect shrill cries from eco-extremist crowd demanding that we never, never, never ever send humans to Mars. Not so much in the fear that astronauts could die (who cares, right?) but that evil imperialistic primates would mercilessly genocide peaceful oppressed Mars bacteria.

"The Sun is about halfway through its main-sequence stage, during which nuclear fusion reactions in its core fuse hydrogen into helium. Each second, more than four million tonnes of matter are converted into energy within the Sun's core, producing neutrinos and solar radiation. At this rate, the Sun has so far converted around 100 Earth-masses of matter into energy. The Sun will spend a total of approximately 10 billion years as a main-sequence star."

And, "The increase in solar temperatures is such that in about another billion years the surface of the Earth will likely become too hot for liquid water to exist, ending all terrestrial life."
From: Sun
At: http://en.wikipedia.org/wiki/Sun



"In 1.1 billion years from now, the Sun will be 10% brighter than it is today. This extra energy will cause a moist greenhouse effect in the beginning, similar to the runaway warming on Venus. But then the Earth’s atmosphere will dry out as the water vapor is lost to space, never to return."
From: Life of the Sun  By Fraser Cain on March 10, 2012
At: http://www.universetoday.com/18847/life-of-the-sun/



Maybe "never, never, never" is too long a period of time.

If we want to save "peaceful oppressed Mars bacteria" we will need to take them, or their genetic codes, with us as we eventually retreat outward from both Mars and the Earth.



"Over 98% of documented species are now extinct,[2] but extinction occurs at an uneven rate."
From: Extinction event
At: http://en.wikipedia.org/wiki/Extinction_event


Since over 98% of all the previous species on our planet are now extinct, perhaps we shouldn't wait too long in getting prepared to protect possible Martian species from the sometimes dangerous universe. Maybe we shouldn't wait too long in figuring out how to save Earth's current species either...


Cheers!

[Celebrimbor]

Since over 98% of all the previous species on our planet are now extinct, perhaps we shouldn't wait too long in getting prepared to protect possible Martian species from the sometimes dangerous universe. Maybe we shouldn't wait too long in figuring out how to save Earth's current species either...

This figure is misleading.  It doesn't quite equate to "Watch out! There's only 2% left!"

Much of the 98% are pre-historic things that just wouldn't cope in today's natural environment - they've evolved into other things (i.e. the 2%).

[JohnFornaro]

Since over 98% of all the previous species on our planet are now extinct, perhaps we shouldn't wait too long ...

This figure is misleading.  It doesn't quite equate to "Watch out! There's only 2% left!" ...

Yer right it's misleading.  General statements like this, which appear on the internets so frequently, are meant to increase web page clicks at best, and at worst, to merely instill fear while not imparting knowledge, to no real purpose.

**********

Edit to clarify the idea of "general statements like this".  I saw this statement on the oracle the other day: "one bacterium to weight of the Earth in less than two days dividing every 20 minutes".  It was meant to support a thesis that forward contamination of Mars could have a non-zero chance of rapid, drastic disruption, inside of forty eight hours in the case of a smallish planet.  That thesis is just plain wrong.

This thesis, "since over 98% of all the previous species on our planet are now extinct, perhaps we shouldn't wait too long", variants of which are repeated by many authors in the internets, is also just plain wrong.  It doesn't inform space policy at all, because it implies that there is some urgency to implement a space policy, when there is no such urgency.

[HappyMartian]

Since over 98% of all the previous species on our planet are now extinct, perhaps we shouldn't wait too long in getting prepared to protect possible Martian species from the sometimes dangerous universe. Maybe we shouldn't wait too long in figuring out how to save Earth's current species either...

This figure is misleading.  It doesn't quite equate to "Watch out! There's only 2% left!"

Much of the 98% are pre-historic things that just wouldn't cope in today's natural environment - they've evolved into other things (i.e. the 2%).

Why should today's polluted environment be considered "natural"?


Is the Sun as consistent as we would like it to be?

From: Sun
At: http://en.wikipedia.org/wiki/Sun
"The Sun is currently behaving unexpectedly in a number of ways.[128][129]"

And, "It is in the midst of an unusual sunspot minimum, lasting far longer and with a higher percentage of spotless days than normal; since May 2008."

And, "It is measurably dimming; its output has dropped 0.02% at visible wavelengths and 6% at EUV wavelengths in comparison with the levels at the last solar minimum.[130]"

And, "Over the last two decades, the solar wind's speed has dropped by 3%, its temperature by 13%, and its density by 20%.[131]"

And, "Its magnetic field is at less than half strength compared to the minimum of 22 years ago. The entire heliosphere, which fills the Solar System, has shrunk as a result, thereby increasing the level of cosmic radiation striking the Earth and its atmosphere."



Does the universe sometimes reach out and give us a surprise tap or nasty blow?


From: Russia's Asteroid Problem
At:  http://www.worldcrunch.com/russias-asteroid-problem/5077
"Just over a century ago, one such asteroid actually did make its way here, exploding just above Siberia with the force of multiple nuclear bombs. It could easily have killed scores, but it happily chose an uninhabited area for the blast."

And, "And, "Less deadly guests visit us from the cosmos on a much more regular basis. According to the work of scientists from the Institute of Astronomy at the Russian Academy of Sciences, the biggest tragedy related to an asteroid in all of recorded human history happened in 1490, when one fell in a city in the Chinese province of Shaanxi and killed more than 10,000 people."


Could an endangered species or two have died off if either event had occurred at a fragile and isolated environment?



Note also:
 
Asteroid 2012 LZ1 Just Got Supersized  By Ian O'Neill  June 22, 2012
"This particular asteroid may not have been a danger, but much of the concern was rooted in the late warning of its detection -- 2012 LZ1 was spotted only four days before closest approach."

And, "So, in the aftermath of the flyby, astronomers at the famous Arecibo Observatory in Puerto Rico used radar to image the interplanetary interloper (pictured top). What they uncovered was a surprise: Asteroid 2012 LZ1 is actually bigger than thought... in fact, it is quite a lot bigger. 2012 LZ1 is one kilometer wide (0.62 miles), double the initial estimate."

And, "Interestingly, this news coincided with Thursday's Space Hangout, when Fraser Cain (Universe Today), Alan Boyle (MSNBC/Cosmic Log), Amy Shira Teitel (Discovery News/Vintage Space), Mike Wall (SPACE.com) and myself meandered into talking about the importance of increased asteroid detection funding:"



Sudbury Basin
At: http://en.wikipedia.org/wiki/Sudbury_Basin
"The Sudbury basin formed as an impact from a bolide approximately 10–15 km (6.2–9.3 mi) in diameter that occurred 1.849 billion years ago[2] in the Paleoproterozoic era."

And, "Models suggest that for such a large impact, debris was most likely scattered globally,[4] but has since been eroded away. Its present size is believed to be a smaller portion of a 250 km (160 mi) round crater that the bolide originally created."



See also: Repeated Blows by Luann Becker
At: http://www.miracosta.edu/home/kmeldahl/articles/blows.pdf



From: Eastern Mediterranean event
At: http://en.wikipedia.org/wiki/Eastern_Mediterranean_event
"The Eastern Mediterranean Event was a high-energy aerial explosion over the Mediterranean Sea, around 34°N 21°E (between Libya and Crete, Greece) on June 6, 2002.[1] This explosion, similar in power to a small atomic bomb, has been related to an asteroid undetected while approaching the Earth."

And, "The event occurred during the 2001–2002 India–Pakistan standoff, and there were concerns by General Simon Worden of the US Air Force that a similar explosion could have sparked a nuclear war between the two countries, had it exploded over Pakistan or India, which would have devastated both regions, causing deaths numbering over 10 million."



From: Neocatastrophism
At: http://en.wikipedia.org/wiki/Neocatastrophism
"Neocatastrophism is the theory that life-exterminating events such as gamma-ray bursts have acted as a galactic regulation mechanism in the Milky Way upon the emergence of complex life in its habitable zone.[1][2][3] It is proposed as an explanation of Fermi's paradox since it provides a mechanism which would have delayed the otherwise expected advent of intelligent beings in the local galaxy nearby to Earth. This is an avenue to explain why none so far have been detected by humans."



NEO air burst explosions and impact events of various sizes need to be carefully considered by farsighted folks everywhere. There may also be a few other types of unknown dangers to possible Martian species and to those species that currently live on Earth.


Cheers!

[HappyMartian]

Since over 98% of all the previous species on our planet are now extinct, perhaps we shouldn't wait too long ...

This figure is misleading.  It doesn't quite equate to "Watch out! There's only 2% left!" ...

Yer right it's misleading.  Statements like this are meant to increase web page clicks at best, and at worst, to merely instill fear while not imparting knowledge, to no real purpose.

OK John. Yep, fear is an inappropriate response, numerous extinct species are still with us, and we should ignore or dismiss whatever is uncomfortable. I now rest assured that extinction events have never happened on Earth or Mars, nor could such dastardly things ever happen in the near or distant future.



Repeated Blows By Luann Becker
At: http://www.miracosta.edu/home/kmeldahl/articles/blows.pdf
"Most people are unaware of it, but our planet is under a constant barrage by the cosmos. Our galactic neighborhood is littered with comets, asteroids and
other debris left over from the birth of the solar system. Most of the space detritus that strikes the earth is interplanetary dust, but a few of these cosmic projectiles have measured five kilometers (about 3.1 miles) or more across."

John, this sounds a bit uncomfortable and Luann Baker also notes, "Based on the number of craters on the moon, astronomers estimate that about 60
such giant space rocks slammed into the earth during the past 600 million years. Even the smallest of those collisions would have left a scar 95 kilometers (about 60 miles) wide and would have released a blast of kinetic energy equivalent to detonating 10 million megatons of TNT."

And, "As researchers continue to detect impact tracers around the world, it’s looking more like impacts are the culprits of the greatest unresolved murder mysteries in the history of life on earth."



Yikes! But impacts wouldn't affect the prospects of early life on Earth or Mars, right? No extinctions, right? Santa wouldn't allow it, would he? That "98% of all the previous species on our planet are now extinct" is simply a method "to increase web page clicks at best, and at worst, to merely instill fear while not imparting knowledge, to no real purpose", right? It obviously adds no context or insight to the question So What if We Found Evidence of Past or Current Life on Mars?

If water was available on Mars and Earth at around the same time, the "detrital zircons with ages as ancient as 4.4 Gyr and their presence implies the existence of a fairly widespread ocean" on early Earth and may also mean that the optimal window for the evolution of life on the Red Planet is larger than "300 My" and may have extended from 4.4 billion years to 3.5 billion years ago because that ancient Martian life might have been somewhat protected from the effects of the Late Heavy Bombardment in the depths of the early Martian oceans and in groundwater deep beneath the surface. And yes, the same situation may have occurred on Earth.

A possible 900 million year long "optimal window for the evolution of life" might produce some interesting results. If life is still active in the deep groundwater, it may not have even 'noticed' the surface conditions during the last few billion years. 

A lot would depend on whether the LHB effectively sterilised the surface or prevented life getting established at all.

Even if liquid water existed through the LHB it might have been too hot to sustain life, as shown in the studies of Jones et al. http://www.astrobio.net/exclusive/3499/water-water-everywhere-but-not-all-drops-have-life

This question would be very hard to answer on Earth, but easier on Mars

[/quote]



From: MARS AND THE LATE HEAVY BOMBARDMENT: 2011 UPDATE. By D. M. Burt, L. P. Knauth, and K. H. Wohletz
At: http://www.planetarycraterconsortium.nau.edu/BurtPCC2.pdf
"Much current and past geological literature on Mars tends to minimize the effects of cratering, or implicitly assumes that the bombardment of Mars was diffusely continuous from its formation at about 4.5 Ga until about 3.5 Ga, an interval called the Noachian. In light of the LHB model, the Noachian interval of Mars may actually have been quite short, with the record of the first half-billion years having been largely destroyed or buried."

"Mars is still an impact-dominated planet, and many of its most interesting features apparently date from and could have resulted directly from the LHB."



From: Noachian
At: http://en.wikipedia.org/wiki/Noachian
"The Noachian is a geologic system and early time period on the planet Mars characterized by high rates of meteorite and asteroid impacts and the presence of abundant surface water."

And, "The lunar cratering record suggests that the rate of impacts in the inner solar system 4000 million years ago was 500 times higher than today.[32] During the Noachian, about one 100-km diameter crater formed on Mars every million years,[2] with the rate of smaller impacts exponentially higher.[33] Such high impact rates would have fractured the crust to depths of several kilometers[34] and left thick ejecta deposits across the planet’s surface."

"Large impacts would have profoundly affected the climate by releasing huge quantities of hot ejecta that heated the atmosphere and surface to high temperatures.[35] High impact rates probably played a role in removing much of Mars’ early atmosphere through impact erosion.[36]"

And "By analogy with the Moon, frequent impacts produced a zone of fractured bedrock and breccias in the upper crust called the megaregolith.[38] The high porosity and permeability of the megaregolith permitted the deep infiltration of groundwater. Impact-generated heat reacting with the groundwater produced long-lived hydrothermal systems that could have been exploited by thermophilic microorganisms, if any existed."

And, "Computer models of heat and fluid transport in the ancient Martian crust suggest that the lifetime of an impact-generated hydrothermal system could be hundreds of thousands to millions of years after impact.[39]



Well, I could go on and gather some more "web page clicks", but maybe it would be better to dive into the Internet and see if anyone wrote something interesting about any of the effects of the Sun's evolution and variability over the last 4.57 billion years and how that may have had an effect on possible early Martian life. 


From: Sun
At: http://en.wikipedia.org/wiki/Sun
"The Sun is currently behaving unexpectedly in a number of ways.[128][129]"

And, "Its magnetic field is at less than half strength compared to the minimum of 22 years ago. The entire heliosphere, which fills the Solar System, has shrunk as a result, thereby increasing the level of cosmic radiation striking the Earth and its atmosphere."



Yup, those poor chemicals on Mars that were struggling to form life may have had to put up with overly friendly asteroids and comets and also periodic variations in both temperature and cosmic radiation. Maybe life has been and always will be a bit of a struggle.


Take care John!   

[JohnFornaro]

Since over 98% of all the previous species on our planet are now extinct, perhaps we shouldn't wait too long ...

This figure is misleading.  It doesn't quite equate to "Watch out! There's only 2% left!" ...

Yer right it's misleading.  Statements like this are meant to increase web page clicks at best, and at worst, to merely instill fear while not imparting knowledge, to no real purpose.

OK John. Yep, fear is an inappropriate response, numerous extinct species are still with us, and we should ignore or dismiss whatever is uncomfortable. I now rest assured that extinction events have never happened on Earth or Mars, nor could such dastardly things ever happen in the near or distant future.

Furthermore, an inadequate analysis would conclude that an unnamed someone on this thread, actually proposes such a head in the sand outlook.  I don't mind snark in principle, but I do insist that it be grounded in logic.

Based on the number of craters on the moon, astronomers estimate that about 60 such giant space rocks slammed into the earth during the past 600 million years.

Yikes! But impacts wouldn't affect the prospects of early life on Earth or Mars, right? No extinctions, right? Santa wouldn't allow it, would he? That [per JF], "98% of all the previous species on our planet are now extinct" is simply a method "to increase web page clicks at best, and at worst, to merely instill fear while not imparting knowledge, to no real purpose", right? It obviously adds no context or insight to the question So What if We Found Evidence of Past or Current Life on Mars?

Here's your mistake, in case you're interested.

The methodology of spreading FUD in order to "increase web page clicks at best" is not yours and yours alone.  You confuse the mere proximity of my remarks to yours as some kind of indictment from me to you, and fail completely to see that the internets is full of such alarum, and that the FUD I refer to "merely instills fear while not imparting knowledge, to no real purpose".

In other words, to paraphrase Ms. Atreides of sci fi, "I hold up a coat of general description, and you claim a perfect fit".  IOW, "statements like this", are not by definition, "your statement and your statement alone".

I did edit my remark to make this clearer, BTW.

In general, as you say, such extinction events, on the gological time scale are certainly deadly events.  Fortunately, the universe, generally speaking is a "cleaner" one these days, and getting cleaner, thanks to the ever present effect of gravity.  Our own Moon has taken the bullet for us a number of times, no doubt.

The only reason to colonize Mars is because we want to.  It's a good idea, I'd say, to increase humanity's chances of survival, but that would be a beneficial side effect of colonization, not the prime reason for making the attempt.  YMMV.

I don't see any good reason to change my current, long standing position to be on the lookout for these objects.  If you pay no attention to my narrative, that's fine, but you'll be lost in that crowd.

The general observation of the "98%" extinction rate here on Earth adds minimal context and insight to a discussion about the policies and mission prioritizations needed if it is seriously considered that we should colonize Mars.  The reason this is true is because the observation does not indicate a way forward with colonization.

A possible 900 million year long "optimal window for the evolution of life" might produce some interesting results.

"Might", not "does".  What are the policy implications of this "might"?

Clearly, we should be looking for life on Mars, and then determine if it is related to us, or if it should represent a "second genesis".  Currently NASA is searching only for "signs of life", and that search is  budgetarily constrained, partially by NASA's own doing in moving the goalposts further and further afield to Europa, and not focusing on the effort to find it where they're looking for it.

[HappyMartian]

...

A possible 900 million year long "optimal window for the evolution of life" might produce some interesting results.

"Might", not "does".  What are the policy implications of this "might"?
...

The "might" indicates a possibility of early life. As to the Space Cadet policy implications, my perspective is simple: Get back to the Moon ASAP with as many humans and robots as possible. Build a permanent Lunar base. Everything we need and want to do in space, including humans doing in depth exploration on Mars and devising a robust layered defense of Earth against NEOs, would get a lot easier with Lunar ISRU.

Life on Mars may exist or have been destroyed either recently or long ago by a series of impact events or some other wobble of the cosmic wheel. Nonetheless, we shouldn't wait to see how long our own luck is going to last and should promptly get to work on building a Lunar home. 

The Boy Scout motto is the lesson we should learn in considering the cratered faces of both Mars and the Moon. "Be Prepared."

If there is no life on Mars, treasure life on our planet.
If there once was life on Mars, treasure life on our planet.
If there currently is life on Mars, treasure life on our planet and on Mars.

Unfortunately, currently we are not well prepared to do very much in space and that fact intertwined with our bickering over nonsense seems to indicate we don't treasure life on our own planet, let alone any life on Mars.

However, persistence pays off, so we will persist in expanding the sphere of human activities in space. The ISS, Curiosity rover, Shenzhou 9 and Tiangong 1, Dawn, and many more active and historical space missions do give one reasonable hope that our space capabilities will one day begin to match our dreams and vanquish some of our fears.


Cheers!


Edited.