Right now all our missions to Mars are sterilized to protect it from any Earth life that could hitch a ride and confuse the searches. This report by the Planetary Protection Independent Review Board is a proposal to treat most of Mars similarly to the Moon for planetary protection. We would no longer need to sterilize rovers that we send to large regions of Mars, just document what they do. The suggestion is to reclassify them as Category II:

where there is only a remote chance that contamination carried by a spacecraft could jeopardize future exploration. In this case we define remote chance as the absence of niches (places where terrestrial microorganisms could proliferate) and/or a very low likelihood of transfer to those places.

COSPAR Workshop on Planetary Protection for Outer Planet Satellites and Small Solar System Bodies European Space Policy Institute (ESPI), 1517 April 2009

The report comes with a cover letter from NASA recommending to their planetary protection officer that they implement the proposal:

This would be fine if we had clear evidence that these regions are like the Moon. However, we don't. The report relies on an earlier 2014 report that is now out of date. Even when it was in process of publication, NASA and ESA took steps to get it independently reviewed. For some reason they cite this problematical report, but don't cite the critical 2015 review of it. This meme summarizes one of the main issues:

Its important to get this right as there is no way to do a do over. It would be so sad to get to Mars, find life there, and then realize it was just life we brought ourselves. For many, the search for other lifeforms in our solar system is one of the major motivating reasons to explore Mars and other parts of our solar system with a potential for life.

Also if we find life based on a different biochemistry - this can be the basis of billion dollar industries in the future (as is already the case for enzymes from extremophiles). For details see Billions of dollars commercial potential of extraterrestrial biology.

This article will focus on the forwards direction, the risk of sending Earth microbes to Mars because the legal protection in that direction is very weak. But first lets look at the backwards direction.

Here is a video I made for this article (while working on the draft)

(click to watch on Youtube)

skip to What about the forwards direction?

In the backwards direction from Mars to Earth, we are strongly protected by many environmental laws and laws to protect human health that we didnt have at the time of Apollo. These laws dont rely on the Outer Space Treaty for their legal basis. How NASA categorizes Mars makes no difference to them. See the article by Margaret Race of the SETI institute.

NASA is going to send a sample caching rover to Mars in 2020 and they hope to send a second mission in the 2020s to return some of these samples back to Earth for analysis. They plan to return them unsterilized (a sterilized sample would not trigger environmental laws, but would be just like the sample returns from meteorites, comets, and the Moon).

I cant find any evidence that NASA have made a start on preparing the legislation. They havent left enough time to complete this process within their desired timescale, indeed, they probably should have started in 2010 or earlier if they want a sample return by 2030. There are papers about the engineering challenges of the sample return mission, but I can't find anything about the legal processes (if you know of anything do say in the comments).

Mars sample return concept - credit NASA. If NASA wants to return an unsterilized sample by 2030 they should have started the legal preparation for this about a decade ago at the latest. There is no sign they have even done any planning for the legal process yet.

Perhaps they expect it to be like Apollo 11 where they published the sample return precautions as an informal document on the day of the launch to the Moon and didnt go through any proper legal process? This would not be permitted today.

Mars could have extraterrestrial life there. Its not known to be sterile, and the dust can carry spores almost anywhere on the planet (more on this later).

As well see new discoveries have opened up the possibility of native microbial life on Mars hidden from our orbital telescopes just centimeters below the dust. This may be possible even in the exceedingly dry tropical areas where Curiosity is roving, especially if martian life has a biochemistry adapted to lower temperatures than Earth life.

Some Mars colonization enthusiasts and space engineers will tell you that any life we find on Mars will be from Earth, but they have not persuaded the astrobiologists of this. The designers of instruments to look for indigenous life there are careful not to make any assumptions about its biochemistry or whether it is related to Earth life.

We cant assume that any life in a sample returned from Mars is related to Earth life unless we have studied it already on Mars.

This life could also be hazardous to humans or our biosphere. To take a simple example, legionnaires disease is an infection of biofilms that can use the same methods to infect human lungs, seeing it as a warm biofilm - it is not adapted to humans. Some strains of it are now adapting to our environments, spread by humans infected by it, but the same could happen with Martian life that invades the lungs of an astronaut.

Astrobiologists say that though it is possible that Mars life could be mystified by an alien biochemistry, its also possible that it hasnt evolved any resistance to it, never having encountered it before. Joshua Lederberg put it like this:

"If Martian microorganisms ever make it here, will they be totally mystified and defeated by terrestrial metabolism, perhaps even before they challenge immune defenses? Or will they have a field day in light of our own total naivete in dealing with their aggressins?

from: "Paradoxes of the Host-Parasite Relationship"

Our lungs might offer no resistance, not even recognizing it as life as it munches away at them, and with a different biochemistry they would be likely to be naturally resistant to our antibiotics, which target particular processes of the pathogens. There would also be risk of larger scale environmental disruption, even if harmless to humans. As the National Research Council put it in 2009:

The risks of environmental disruption resulting from the inadvertent contamination of Earth with putative martian microbes are still considered to be low. But since the risk cannot be demonstrated to be zero, due care and caution must be exercised in handling any martian materials returned to Earth

Assessment of Planetary Protection Requirements for Mars Sample Return Missions

These reports haven't gone into details of how the environment could be disrupted. To give some points to think over right away (I will come back to this later), would our ecosystems work the same way if half the microbes were mirror DNA, say, or PNA, or TNA, or had novel amino acids that Earth life doesn't use, or didn't use proteins, to give a few examples? Would the martian life be edible? Would it have nutritional value? What about accidental poisons, like the way that cyanobacteria can kill dogs and cows? If it's a different biochemistry, they seem unlikely to be exact "drop in" replacements to terrestrial microbes, so there would be changes in how they function. Higher lifeforms would adapt more slowly than the microbes, with their longer lifespans.

The legislators would not ignore arguments such as these. There would be extensive public debate, and Earth would be protected.

I used Margaret Races article in an attempt to work out a timeline here for return of an unsterilized sample with potential for microbial life of an unknown alien biochemistry. I assumed that there were no objections to delay the legal process. Even with that assumption, I dont see how it can be done before 2040, if you start the legal process today. This takes into account the likely time requirements for constructing the receiving facility, based on the previous sample return studies. NASA would not start the expensive build (half a billion dollars facility) until it knows what it is legally required to do.: Why we are unlikely to return an unsterilized sample before 2040. These laws don't depend on the wording of the Outer Space Treaty in any form, but are independent legislation to protect Earth.

For these reasons Im not concerned about the backwards direction as far as safety is concerned. I expect NASA to sterilize their sample if they do return those samples from Mars to Earth, or return them to somewhere isolated from contact with Earth, such as a satellite set up for telerobotic study of the sample above GEO. They can use either of those approaches within the Outer Space Treaty. If there is no possibility of an unsterilized sample contacting Earth's biosphere, or Earth entering into the chain of contact with an unsterilized sample, it wouldn't trigger this legislation to protect our Earth.

The main concern is for the forwards direction. There isnt any other legislation here to protect Martian life apart from the very weak Outer Space Treaty. It is based on a few phrases about harmful contamination.

If these proposals were adopted in the forwards direction, you could send what you like to these regions of Mars, tardigrades, and extremophile blue green algae that have already been tested in Mars simulation chambers. The only requirement would be to document what you do. Eventually you could send humans too, with this category II classification, though returning them would be another matter if they had made contact with extraterrestrial microbes on Mars.

The report is here together with a cover letter from NASA recommending to their planetary protection officer that they implement the proposal:

This new report has few cites. Incongruously, its lead author is a planetary geologist.

One of their main cites is a report from 2014 by Rummel et al which proposed the use of maps to divide Mars into special regions which need especially careful planetary protection measures such as was used for the Voyager landers in the 1970s, and others that have less stringent requirements such as is used for Curiosity:

This is the basis for their proposal that Mars could be subdivided into regions some reclassified as category II. Although they dont go into detail, presumably they would use a map like the one in the 2014 review, and classify all except the uncertain regions as category II:

Map from the 2014 report. Purple is low in elevation, and grey is higher elevation. Red and blue lines delineating regions are approximately 50 km in width

In the text overlay I summarize the objection to this map in the 2015 review "2014 map of uncertain regions of habitability. 2015 review says maps can only represent incomplete knowledge."

They dont mention the problems identified with the use of maps in the 2015 review.

Even before Rummel et als report was published, both NASA and ESA took steps to have it reviewed independently.

This 2015 review overturned several of the findings of the 2014 report, and in particular, it recommended against the use of maps [49] saying:

In general, the review committee contends that the use of maps to delineate regions with a lower or higher probability to host Special Regions is most useful if the maps are accompanied by cautionary remarks on their limitations. Maps [of] surface features can only represent the current (and incomplete) state of knowledge for a specific timeknowledge that will certainly be subject to change or be updated as new information is obtained.

5 Generalization of Special Regions and the Utility of Maps

This new NASA report doesnt mention the 2015 review. Its an extraordinary omission from a report that is recommending the use of maps for category II.

I dont know the reason for this omission. They certainly should have looked at this 2015 review, and not just at the original 2014 report, before making this recommendation to NASA to map out large parts of Mars as category II like the Moon.

The 2015 report used the example of Recurring Slope Lineae (RSLs) to explain why maps are not enough by themselves. These are seasonal streaks that form on sun facing Martian slopes. They appear in the Martian spring, grow and broaden through the summer and fade away in autumn.

These dark features are not themselves damp and may be dust flows. However, they are associated with hydrated salts and they may also be linked with salty water (brines) in some form. Sadly the HiRISE instrument can only observe them in the early afternoon locally, the driest time for the Martian surface, because of its high inclination sun synchronous orbit. This makes it especially hard to know if there are any brines moving down these slopes.

Warm Season Flows on Slope in Newton Crater (animated)

The first ones were found in higher latitudes, but many of these have now been found in the Martian tropics, especially on the slopes of the Valles Marineres. Their status is unknown, whether they could have habitats for Earth life or not. At present they are classified as

As such they meet the criteria for Uncertain Regions, to be treated as Special Regions. [a Special region is one that Earth microbes could potentially inhabit]

The 2015 review gives the example of the ExoMars Schiaparelli lander. All HiRISE images of the landing site were inspected for the possible presence of RSL's. [50]

As another example of this, 58 RSLs were found on Mount Sharp close to the Curiosity landing site.

Here are some of them:

Possible RSLs on mount Sharp not far from the Curiosity rover. These photos are taken at a similar time in the Martian year, they are less prominent in the earlier one in 09 March 2010 and more prominent with some new ones in the later image August 6 2012. Photo from supplementary information for Transient liquid water and water activity at Gale crater on Mars

Importantly, these were not discovered until after the Curiosity landing in 2012. See Slope activity in Gale crater, Mars (2015) and Nature article: Mars contamination fear could divert Curiosity rover

This shows that we mightnt always be able to rule out potential uncertain regions that could be habitats at a landing site. They may be discovered later, after the landing itself.

More RSLs have been found in the Mawrth Vallis region, one of the two final candidates for ExoMars landing site

These results denote the plausible presence of transient liquid brines close to the previously proposed landing ellipse of the ExoMars rover, rendering this site particularly relevant to the search of life. Further investigations of Mawrth Vallis carried out at higher spatial and temporal resolutions are needed to , to prevent probable biological contamination during rover operations,

Discovery of recurring slope lineae candidates in Mawrth Vallis, Mars

ExoMars isnt going to Mawrth Vallis, because they chose the other candidate Oxia Planum. I cant find anything about RSLs in Oxia Planum, but how confident can we be that this doesnt have RSLs or other potential habitats? Does non detection so far mean they arent there?

This new report also doesnt mention the long running and vigorous debate on the topic of whether we should relax sterilization requirements for spacecraft sent to Mars.

This debate started in two Nature articles in 2013 and has continued in Astrobiology journal through to 2019.

Both sides in this debate were in agreement that there is a significant possibility that Earth microbes can contaminate Mars.

Surely neither side in this debate would support classifying most of Mars as category II like the Moon.

Rather, the argument in Nature and Astrobiology journal is about whether we should reduce sterilization requirements for Mars in order to study these potential habitats quickly before human missions get there and make it impossible to study them in their pristine condition without Earth life.

The other side in this debate argue that we have a fair bit of time before humans get there, and that if we relax planetary protection we risk finding Earth microbes we brought there ourselves.

Those arguing for relaxing planetary protection are:

Against

This debate is not mentioned in this report.

Nor does it mention the many new potential surface or near surface habitats that have been proposed / indirectly detected / theorized since 2008. We have had more of these than there have been years since 2008.

The 2014 report briefly considers these. The 2015 review expands on this topic, and says that to identify such potential habitats requires a better understanding of the temperature and water activity of potential microenvironments on Mars, for instance in the interior of craters, or microenvironments underneath rocks. These may provide favourable conditions for establishing life on Mars even when the landscape-scale temperature and humidity conditions would not permit it. [46]

The 2014 report looked at distributions of ice and concluded that ice in the tropics is buried too deep to be a consideration[47]

However the 2014/5 review corrected this due to evidence of ice present at depths of less than one meter in pole-facing slopes[48]

Research since then still hasnt resolved these issues.

Even the 2014 report acknowledged limitations:

"Claims that reducing planetary protection requirements wouldn't be harmful, because Earth life can't grow on Mars, may be reassuring as opinion, but the facts are that we keep dis4g life growing in extreme conditions on Earth that resemble conditions on Mars. We also keep discovering conditions on Mars that are more similarthough perhaps only at microbial scalesto inhabited environments on Earth, which is where the concept of Special Regions initially came from."

"A New Analysis of Mars "Special Regions": Findings of the Second MEPAG Special Regions Science Analysis Group (SR-SAG2)" (PDF).

Id like to cover a couple of these potential habitats to motivate this, then Ill look at why it is so important to protect Mars from Earth life - is it really so important to make sure we dont mix Earth life with Mars life before we canstudy it?

Nilton Renno's droplets that form where salt touches ice - why did he call a droplet of salty water on Mars "a swimming pool for a bacteria"?

This is perhaps one of the most striking discoveries in recent years because of its implications for habitability of Mars. Nilton Renno found that liquid water can form very quickly on salt / ice interfaces. Within a few tens of minutes in Mars simulation

experiments.

Erik Fischer, doctoral student at University of Michigan, sets up a Mars Atmospheric Chamber on June 18, 2014. These experiments showed that tiny "swimming pools for bacteria" can form readily on Mars wherever there is ice and salt in contact.

This is striking as it could open large areas of Mars up as potential sites for microhabitats that life could exploit. The professor says

"If we have ice, and then the salt on top of the ice, in a few tens of minutes liquid water forms. Our measurements clearly indicate that. And it's really a proof that liquid water forms at the conditions of the Phoenix landing site when this salt is in contact with the ice.

"Based on the results of our experiment, we expect this soft ice that can liquefy perhaps a few days per year, perhaps a few hours a day, almost anywhere on Mars. So going from mid latitudes all the way to the polar regions.

" This is a small amount of liquid water. But for a bacteria, that would be a huge swimming pool - a little droplet of water is a huge amount of water for a bacteria. So, a small amount of water is enough for you to be able to create conditions for Mars to be habitable today'. And we believe this is possible in the shallow subsurface, and even the surface of the Mars polar region for a few hours per day during the spring."

(transcript from 1:48 onwards)

(click to watch on Youtube)

That's Nilton Renno, who lead the team of researchers. See also Martian salts must touch ice to make liquid water, study shows . He is a mainstream researcher in the field - a distinguished professor of atmospheric, oceanic and space sciences at Michigan University. For instance, amongst many honours, he received the 2013 NASA Group Achievement Award as member of the Curiosity Rover " for exceptional achievement defining the REMS scientific goals and requirements, developing the instrument suite and investigation, and operating REMS successfully on Mars" and has written many papers on topics such as possible habitats on the present day Mars surface.

This was a serendipitous discovery announced in April 2015. Liquid brines that form through deliquescing salts (perchlorates) - the salts take in water from the atmosphere (same principle as the salts you use to keep equipment dry).

They noticed that when Curiosity drives over sand dunes, then the air above them is drier than it is normally. When it leaves the sandy areas the humidity increases.

Rover Environmental Monitoring Station (REMS) on NASA's Curiosity Mars rover

See more here:
Can NASA'S Plan To Treat Parts Of Mars Like The Moon Risk Future Discoveries Of Extraterrestrial Life? - Science 2.0