The "Special Regions" On Mars Where It Is Forbidden To Explore, For Good Reason

NASA and the China National Space Administration (CNSA) have both landed exploratory rovers on Mars, with the aim to understand if life could, or ever has, existed on the Red Planet, our second closest neighbor. 

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While these missions focus on interesting areas of the planet, which may once or still be host to alien life, there are certain regions of Mars that are forbidden by space treaties to explore. These areas, known as "special regions", as well as the lesser "uncertain regions", would be a bad idea to explore, despite being some of the more interesting places to conduct scientific research on this world.

During the height of the 20th-century "space race", the United States, the Soviet Union, and (for some reason) the United Kingdom signed the UN Outer Space Treaty of 1967. This key document in space history forbade all nations that signed up to it from claiming sovereignty over any celestial bodies, establishing military bases upon them, and using nuclear weapons upon them. (The latter rule did not deter the US from recently exploring the idea of nuking the Moon).

In the treaty, there were other important specifications. One reason why humanity is so keen to explore the big, dark beyond is the tantalizing possibility of finding other lifeforms out there. This is an incredibly difficult task, given the distances involved and the complexity of such missions. One complication is, if we were to find evidence of life on another planet, such as Mars, how would we know we didn't bring it there? A false positive for life would be a nightmare, but there is also a second concern: How do we ensure that we do not contaminate an alien planet with our own life?

For these reasons, the UN Outer Space Treaty included a section forbidding potentially hazardous exploration of Solar System bodies:

“States Parties to the Treaty shall pursue studies of outer space, including the Moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter, and where necessary, shall adopt appropriate measures for this purpose.”

Since then, as we have learned more about Mars and its potential suitability for ancient and current life, more steps have been taken to agree about where can, and cannot, be explored on the planet. The Committee on Space Research (COSPAR) of the International Council for Science has been key in creating these guidelines and identifying the "special regions" on the planet where it should be forbidden to land.

"High-priority science goals, such as the search for life and the understanding of the martian organic environment, may be compromised if Earth microbes—that is, prokaryotic or eukaryotic single-cell organisms—carried by spacecraft grow and spread on Mars. This has led to the definition of “Special Regions” on Mars where strict planetary protection measures have to be applied before a spacecraft can enter these areas," COSPAR explained following a 2016 investigation, at NASA's request.

"The concept of a Special Region was developed as a way to refer to those places where the conditions might be conducive to microbial growth as we understand this process. In particular, this refers to places that might be warm and wet enough to support microbes that might be carried by spacecraft from Earth."

Included in the definition of a "special region" are places where it is "interpreted to have a high potential for the existence of extant martian life".

In practice, no places on the Red Planet where we could feasibly reach with current missions have been listed as meeting these criteria. But there are areas, known as "uncertain regions", which could potentially be dubbed special regions with more study. These include recurring slope lineae (RSL), or narrow, dark streaks that appear on Mars seasonally. These were thought initially to potentially be signs of flowing water, though more recent research has suggested that they were formed through dry, granular flows. More recently, oceans of water have potentially been identified beneath the planet's surface. But sitting between 11.5 and 20 kilometers (7.1 to 12.4 miles) below the surface, that's inaccessible to any upcoming missions, and difficult to contaminate without a large-scale, sci-fi level drilling operation.

Then there is the announcement this year of potential biosignatures found by Mars rover Perseverance on the Bright Angel formation in Cheyava Falls. As well as ruling out all other explanations, the team must rule out potential contamination from Earth, highlighting the importance of planetary protection and decontamination before sending missions to other planets and moons in our Solar System. The guidelines suggest that before landing a mission on other planets, they should assess whether the area should qualify as a "special" or "uncertain" region.

While some would like for these prohibitive requirements for exploration to be dropped, perhaps to make it easier and less expensive to search for alien life, they are in place for a good reason. Complicating the picture even more is that we keep finding life to be hardier than we once imagined. 

"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 discovering life growing in extreme conditions on Earth that resemble conditions on Mars," a recent paper on the topic explains. "We also keep discovering conditions on Mars that are more similar—though perhaps only at microbial scales—to inhabited environments on Earth, which is where the concept of Special Regions initially came from."

As well as the noble goal of not killing alien life just as we find it, the main concern is that we could not be sure that we have found alien life at all.

"Advocating for unjustified loosening of bioburden controls translates into doing a poor job of life detection and forward contamination control during the robotic exploration of Mars," the paper concludes. "Such an approach is self-limiting and does nothing for future human exploration. Doing so without an informed understanding of the real costs and what is at risk would be ignorant and irresponsible."

For these reasons, it might be best to leave these "special regions" alone, should we identify any candidates. At least until we can be sure hardy Earth life cannot survive the journey to our neighbor.