The Big Martian Maybe

July 11, 2018

Could life exist on Mars?  There’s plenty of compelling evidence that it could, and also plenty of compelling evidence that it could not.  As a result, we’re left with a big, fat maybe. Perhaps the biggest, most frustrating maybe in all of modern science.

After last month’s announcement that the Curiosity rover had found large, complicated organic chemicals on Mars, I was initially tempted to add another point to the “yes, life could exist on Mars” column. But then I read the actual research (which is excellent, by the way).  At this point, I think the only thing we can say for certain is that the big maybe about Mars is even bigger and even more maybe-like.

The Curiosity rover dug up some samples from Martian mudstone, samples that apparently contained organic macromolecules.  What are macromolecules?  For now let’s just say they’re very big molecules.  We can dive into the technical details of what defines a macromolecule in Friday’s episode of Sciency Words.

The problem, as I understand it from that research paper, is that these macromolecules were too big for Curiosity’s instruments to analyze.  So Curiosity destroyed the molecules through a process called pyrolysis (also coming soon to Sciency Words) and analyzed the bits and pieces as they broke apart.  Even those bits and pieces were difficult for Curiosity to study because there were so many of them, but for the most part they seemed to be aromatic compounds made of carbon, hydrogen, and sulfur.

These are the kinds of organic materials that could be deposited on a planet by meteor impacts.  They could also have formed through rather ordinary geological processes.  Or they could be the residue left behind by some kind of biological activity.  And there doesn’t seem to be any way to know for sure where these organics came from based solely on the data Curiosity was able to collect.

So we’re still left with a big maybe.  However, it was once thought by some that the Martian environment was too harsh to preserve these sorts of molecules at all.  Thanks to Curiosity, we now know Mars can and does preserve its organic macromolecules.

And that means that if Mars has had any sort of biological activity, either in the past or present, the chemical record of that activity should be there for us to find.  A definitive yes or no to our question is possible!  We just have to keep digging.

Molecular Monday: Carbon vs. Silicon

June 4, 2018

I recently completed a certain long anticipated manuscript, and I’m currently in the process of rewriting and revising it. Editing this thing has me thinking about a certain line from Macbeth, which I’ll paraphrase as: I have walked so deep into blood that, should I go no farther, returning will be as tedious as continuing onward.

That’s morbid, I know.  What do you expect?  It’s Shakespeare!  But simply replace the word blood with red ink, and I think you’ll understand how the editing is going for me.

Anyway, I’ve waded so far into that “red ink” that I haven’t had much time for research; so for today’s episode of Molecular Monday I thought we’d take a look back at one of my older posts.  A very old post, from all the way back in 2011, long before I really knew what I was talking about with regard to organic chemistry.

And yet despite my ignorance and inexperience, I think I still got the general idea right with this one.  Also, this post includes one of my very first attempts at science illustration, so I hope you’ll enjoy that!


It’s often suggested that the aliens from the Aliens movies, sometimes referred to as xenomorphs, are silicon based rather than carbon based like us.  There are a lot of silicon based aliens in science fiction, but no one knows if such a thing is really possible.

Carbon and silicon have one thing in common: they both have four bonding sites, meaning they can bond with up to four other atoms when making a molecule.  Other than that, they’re completely different.  Silicon is a metalloid; carbon is a nonmetal.  Carbon is much lighter and more flexible, and it’s ten times more abundant in the universe.

If the idea of silicon based life is simply to replace carbon atoms with silicon, it wouldn’t work.  Take breathing for example.  We breath oxygen in, and exhale carbon dioxide.  When a silicon based alien breaths in oxygen, it will have a hard time exhaling silicon dioxide; silicon dioxide is better known as quartz crystal.

I don’t remember any xenomorphs hacking up quartz crystals in the movies, but maybe they use silicon for something else.  Carbon has to be part of their biochemistry anyway, or they wouldn’t be able to grow inside human hosts.

Humans are not only carbon based.  We also depend on oxygen, nitrogen, hydrogen, phosphorus, and sulfur.  Not only that, but we need traces of iron, sodium, potassium, etc as well.  So maybe the xenomorphs can be carbon based and silicon based at the same time.

Sciency Words: Special Region

March 30, 2018

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


It’s been several months now that I’ve been focusing almost all my research efforts on Mars. During that time, I’ve read a lot about those very special regions of Mars that might be home to alien life, but I didn’t realize until last week that “special region” is, in fact, a technical term.

Not only that, it’s a term whose precise definition has been and continues to be in dispute—exactly the kind of term most worthy of a Sciency Words post!

According to this paper from the journal Astrobiology, a special region is any region on Mars where “terrestrial organisms are likely to replicate” or where there is “a high potential for the existence of extant martian life forms.” By international agreement, NASA and other space agencies are not allowed to risk contaminating these special regions with our Earth germs. Since our current Mars rovers may not be 100% germfree, they’re all banned from exploring those areas.

But where are these regions, exactly? What are their boundary lines? This is where the definition of this term gets murky. We just don’t know enough about Mars to know which regions are special and which are not.

Initially I assumed it would be up to the International Astronomy Union (I.A.U.) to sort this out. They claim to be the sole authority on naming, categorizing, and defining space stuff. Even if you’ve never heard of the I.A.U. before, I can almost guarantee you’ve heard about at least one thing they did.

But in this case, I guess because this is a matter of international law, it’s a different organization that has to define what is or is not a special region. That organization is called COSPAR (Committee On SPAce Research), which is part of the International Council for Science. And COSPAR has been understandably reticent about setting any official definitions or drawing any official boundaries on a map. Like I said, we just don’t know enough about Mars yet.

Instead, COSPAR recommends evaluating potential landing sites on Mars on a case-by-case basis, keeping the latest scientific data in mind, to avoid contaminating any regions that might possibly someday turn out to be special (whenever we figure out what that means). According to this article from NASA, COSPAR reviews and updates the definition of “special region” every two years. Their next formal meeting is scheduled for July of 2018.

P.S.: Wait a second… who put that sign there? They better have decontaminated it first!

Mars Rovers Must Rove Responsibly

March 21, 2018

We’ve sent several robotic space probes to Mars already, and several more will be heading to the Red Planet in the next few years. Mars is already the second most heavily explored planet in the Solar System, after Earth.

But our robots are forbidden by international law from entering regions where Martian water appears to be flowing, or regions where Martian life could hypothetically exist. Why? Because there’s a chance that microorganisms from Earth hitched a ride aboard our space probes, survived the journey to Mars, and might start to grow and reproduce if they’re exposed to Martian water.

Yesterday, we talked about a paper in the journal Astrobiology which argued that the risk of contamination is minimal, and we should let our Mars rovers do their jobs. Go explore, and if there’s Martian life, go find it! Today we’re looking at a response to that paper, also published in Astrobiology, in fact in the same issue of Astrobiology. A response which raises several concerns, such as:

  • In the last few decades, we’re learned that Earthly microorganisms can be far more resilient than we ever imagined. Some of them very well might survive—and thrive—on Mars.
  • We’ve also learned that Mars is far less hostile to life than we previously assumed. Quite a few microbes from Earth might find Mars a rather comfortable place to live.

Taken together, these two points suggest that we have not overestimated the risk of contaminating Mars. In fact, we may have drastically underestimated the risks, and we need to be more careful, not less careful, about where we let our Mars rovers go. Otherwise:

  • We might destroy the very Martian life forms that we’re so desperately hoping to find.
  • We might make Mars’s water undrinkable for future human settlers.
  • We might end up misidentifying a stowaway microbe from Earth as a new form of life native to Mars, and the authors of this response paper argue that even our best gene sequencing technology might not be able to clear up the potential confusion.

Even if our Mars rovers keep their distance from Mars’s potentially-habitable or potentially-inhabited areas, there’s still a lot of valuable science they can do, especially when they’re investigating areas that used to be lakes or rivers, areas that could have supported lots and lots of alien life in the past, even if they’re bone dry and very thoroughly lifeless in the present.

So let’s take things slow. Let’s stick to the original plan (and current international agreements) and continue to explore Mars in a responsible and methodical manner.

Or maybe not. Gosh, I don’t know. After reading these two papers back to back, I really don’t know what to think.

Let a Mars Rover Rove

March 20, 2018

In the near future, human beings will probably set foot on the planet Mars. Human beings will likely do a lot of other things on Mars too: coughing, sneezing, peeing, pooping… it won’t be long until Mars is thoroughly contaminated with our germs.

We may have contaminated Mars already, at least a teeny bit, with our robotic space probes. You see, these probes may not have been as thoroughly cleaned and sterilized as they were supposed to be before they left Earth. Consequently, our Mars rovers, like the Curiosity rover, are forbidden from entering or even approaching sites where liquid water may be present.

This is to ensure that we don’t endanger any native Martian life that could hypothetically be living in those watery areas. It’s also to ensure that we don’t misidentify Earth germs as native Martian microbes at some point in the future.

But according to this paper published in the journal Astrobiology, we really should lighten up and let our Mars rovers do their jobs. We’ve spent billions on these robots, and we’re not using them to their best. While there is some risk of contamination, it’s only a small risk, or so the authors of the paper claim.

First off, the Martian environment is extremely cold, there’s lots of radiation, and an abundance of harsh, oxidizing chemicals in the soil. In short, Mars can do a better job sterilizing out space probes than we can. The very few Earth germs that might have made it to Mars thus far wouldn’t be able to spread far.

As for misidentifying an Earth germ as a Martian microorganism, the authors of the paper claim this wouldn’t be a problem. At this point, we have a pretty good idea which Earthly bacteria could have hitched a ride to Mars, because we know which bacteria were later found in the clean rooms where our space probes were built. Those bacteria can be easily identified with gene sequencing.

So let’s send the Mars rovers in. Let them do their jobs. Let them study Mars’s recurring slope lineae and other watery features, or any other areas where life could possibly exist. Let’s do this now, while the risk of contamination is still relatively low, because the humans are coming, and they’re bringing a whole lot more germs with them!

Or maybe not! As I’ve said before, these kinds of scientific papers should be understood not as final declarations of fact but as part of an ongoing conversation among scientists. In tomorrow’s post, we’ll talk about the other side of the argument.

Sciency Words: Astro-Paleontology

December 8, 2017

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:


This may be a first for Sciency Words. Usually I discover new words to share with you during the normal course of my research, but this time I thought to myself, “astro-paleontology has got to be a thing by now,” and then went and found that it is.

Or at least it almost was. Back in the 1970’s, astronomer John Armitage wrote a paper titled “The Prospect of Astro-Palaeontology,” officially coining the term. And then it seems nobody followed up on the idea.

The word paleontology comes from several Greek roots and means the study (-logy) of that which existed (-onto-) in the past (paleo-). It think we’re all familiar with what this really means: digging up the fossilized remains of dinosaurs and other organisms that died long ago. By adding the Greek word for star into the mix (astro-), Armitage created a term for the search for and study of the fossilized remains of life on other worlds.

The blog Astro-Archeology did several posts about Armitage’s work. I recommend checking out all three of these posts:

To be honest, I don’t have a whole lot to add to what Astro-Archeology already wrote on this subject, except that the search for alien fossils on Mars is about to heat up.

None of our current Mars missions are equipped to search for life on the Red Planet, either living or dead. But NASA’s next rover, the Mars 2020 Rover, will be. Specifically, Mars 2020 will be designed to hunt for fossilized microorganisms.

So maybe the term astro-paleontology is due for a come-back.

P.S.: You may have noticed that John Armitage and Astro-Archeology spelled this term as astro-palaeontology and I’m spelling it as astro-paleontology, without the extra a. This is a British spelling vs. American spelling thing.

Sciency Words: Geologic Periods of Mars

November 3, 2017

One of the reasons I write this Sciency Words series is to introduce you to terms that I know (or at least suspect) we’ll be talking about in upcoming blog posts. Right now, I’m just getting started with my special mission to Mars series, so I think this is a good time to introduce you to not one but four interesting scientific terms.

Today, we’re looking at the four major periods of Mars’s geological history (based primarily on this article from ESA and this article from the Planetary Society).

PRE-NOACHIAN MARS (4.5 to 4.1 billion years ago)

This would have been the period when Mars, along with the rest of the Solar System, was still forming.

NOACHIAN MARS (4.1 to 3.7 billion years ago)

This period was characterized by heavy asteroid/comet bombardment, as well as plenty of volcanic activity. Most of the major surface features we see today formed during this time: the Tharsis Bulge, Valles Marineris, several of the prominent impact basins in the southern hemisphere, and also the vast northern lowlands—or would it have been the northern oceans? Also valley networks that formed during this time look suspiciously like river channels.

HESPERIAN MARS (3.7 to 3.0ish billion years ago)

Around 3.7 billion years ago, it seems asteroid and comet impacts on Mars died down, and volcanic activity kicked it up a notch. We also see a lot of surface features called “outflow channels” corresponding to this time, rather than the river-like valleys that appeared during the Noachian. These outflow channels may have been created by sudden and violent floods, which may have been caused by melting ice dams releasing lake water.

AMAZONIAN MARS (3.0ish billion years ago to today)

The Amazonian Period began when the northern lowlands, specifically a region called Amazonis Planitia, was “resurfaced,” covering up any impact craters or other surface features that may have been there before. Mars experts disagree about when this happened, but most estimates seem to be in the neighborhood of three billion years ago. Any obvious volcanic or geologic activity ceased during the Amazonian, and for the most part all of Mars’s water has either frozen solid or evaporated into space.

On Earth, if you want to talk about the age of the dinosaurs, what you’re really talking about is the Mesozoic Era, which is subdivided into the familiar Triassic, Jurassic, and Cretaceous Periods. And so if you’re looking for dinosaur fossils, you need look for Mesozoic Era rocks.

At this point we only have a rough sketch of the geologic history of Mars. We don’t know enough to make the kinds of divisions and subdivisions that we’ve made for Earth. But if you want to go looking for Martian dinosaurs (by which I mean fossilized Martian life of any kind, even if its only microbial) then I can tell this much: look for Noachian and Hesperian aged rock formations. Those are the rocks that would have formed back when Mars still had oceans and lakes and rivers (or at least random, violent floods).

At least, landing near some Noachian and/or Hesperian rocks seems to be a high priority for NASA’s Mars 2020 rover.