Our Place in Space: Jezero Crater

Hello, friends!  Welcome to Our Place in Space: A to Z!  For this year’s A to Z Challenge, I’ll be taking you on a partly imaginative and highly optimistic tour of humanity’s future in outer space.  If you don’t know what the A to Z Challenge is, click here to learn more.  In today’s post, J is for…


Someday, I’d like to help dig up dinosaur fossils.  That’s apparently a thing pretty much anybody can volunteer to do.  Someday, I’d also like to live on Mars.  In the distant future, it may be possible to do both of those things.  Places like Jezero Crater on Mars may be full of ancient Martian fossils!

If you look at satellite images of Jezero Crater, it’s pretty obvious it used to be full of water.  You can see what appears to be a dried-up river bed snaking its way across the Martian landscape.  Where that river meets the crater, there’s a breach in the crater wall and a large river delta where the river would have spilled into the crater basin.

Right now, NASA’s Perseverance Rover is driving around that river delta, scoping the place out, examining the sediments and clays found in the region.

Okay, I may have taken some creative liberties with the cartoon above.  If life ever did evolve on Mars, it would have been short-lived.  All of Mars’s lakes, rivers, and oceans would have dried up fairly early in the planet’s history.  It is highly unlikely that anything as complex as fish or seaweed could have developed, and there certainly wouldn’t have been anything as awesome as a Martian dinosaur.

But in places like Jezero Crater, simple microorganisms could have been plentiful.  These microbes may even have joined together, creating larger structures like the bacterial mats we sometimes find here on Earth.  That’s kind of icky, I know, but it could have happened, and those bacterial mats may still be there, preserved as fossils beneath all that red dust.

I don’t expect questions about life on Mars (past or present) to be answered any time soon.  Even if one of our Mars rovers did stumble upon something that looked like a fossilized bacterial mat, there would be scientific debates for years—decades, even—over what that fossil-looking-thing really is and what it’s presence on Mars really means.  We’ve been through this before, when scientists found “bacteria shaped objects” inside a Martian meteorite.  Something can look like a fossilized bacterium, and yet not be a fossilized bacterium.

But someday in the distant future, we will know, one way or the other, if life ever existed on the Red Planet.  And perhaps in that distant future, humans living on Mars will volunteer to help dig up fossils in Jezero Crater, or other places very much like it.

Want to Learn More?

Here’s an interactive map from NASA showing the Perseverance Rover’s current location.  You’ll have to zoom out a little to see all of Jezero Crater.  If you do, you’ll see that the dried-up river (marked Neretva Vallis) and river delta I mentioned are pretty obvious.

And here is a NASA press release from a few years back, announcing Jezero Crater as the Perseverance Rover’s landing site and explaining why the crater was selected.

Also, here’s an article from Space.com about that Martian meteorite I mentioned, the one with those “bacteria shaped objects” inside.

Our Place in Space: HAVOC

Hello, friends!  Welcome to Our Place in Space: A to Z!  For this year’s A to Z Challenge, I’ll be taking you on a partly imaginative and highly optimistic tour of humanity’s future in outer space.  If you don’t know what the A to Z Challenge is, click here to learn more.  In today’s post, H is for…


Venus is my favorite planet.  If you’ve been reading this blog for a while, you probably already know this about me.  The Venusian atmosphere is weird and chemically complex.  The surface is mysteriously smooth, hinting at some pretty extreme geological activity.  And did you know Venus is spinning the wrong way?  She rotates clockwise where every other planet in our Solar System has counterclockwise rotation.  In many ways, I feel like Venus is the planet with the most personality (aside from Earth, of course).  So if there’s a realistic possibility of humans colonizing Venus one day, nothing would please me more!

HAVOC stands for High Altitude Venus Operational Concept.  It’s NASA’s very preliminary plan for exploring Venus, first with robots, then with astronauts, with the eventual goal of establishing a permanent human presence.  Most people scoff at the idea of sending humans to Venus.  Surface conditions are hellish.  The surface temperature is 475 degrees Celsius (900 degrees Fahrenheit).  Atmospheric pressure is 90 times greater than what we experience here on Earth.  Sulfuric acid falls from the sky as rain, and don’t forget about that extreme geological activity I mentioned.  Nobody’s sure what’s happening, but the ground is too smooth, as if it gets regularly “repaved” with fresh lava.

But HAVOC would not involve putting boots on the ground.  Instead, astronauts would explore Venus from the safety of blimps and other airborne habitats.  At an altitude of 55 kilometers above the surface, Venus is quite nice.  You might even call it heavenly.  The temperature and pressure are roughly Earth-normal.  We’d experience Earth-like gravity, too, and Venus would provide almost Earth-like protection from solar and cosmic radiation (a service that the Moon and Mars do not offer).  Also, 55 kilometers up, we wouldn’t have to worry about the sulfuric acid rain; we’d be above the layer of sulfuric acid clouds!

Obviously this is not happening any time soon.  The people at NASA seem to have their hearts set on returning to the Moon in the near future, with a long term goal of getting to Mars.  Still, the idea of exploring Venus with blimps makes sense.  In some ways, Venus might end up being a better second home for humans than Mars—just so long as we stay at that 55 kilometer altitude.

So in the distant future, when humanity is spreading out across the Solar System, don’t be surprised if large numbers of people live in Cloud City-like habitats on Venus.

Want to Learn More?

Check out this paper from the American Institute of Aeronautics and Astronautics, detailing HAVOC as a five phase plan to explore and colonize Venus.

Also, here’s a video from NASA showing what a HAVOC mission might look like, from first arrival in Venusian orbit to safe return back on Earth.

Our Place in Space: The DART Mission

Hello, friends!  Welcome to Our Place in Space: A to Z!  For this year’s A to Z Challenge, I’ll be taking you on a partly imaginative and highly optimistic tour of humanity’s future in outer space.  If you don’t know what the A to Z Challenge is, click here to learn more.  In today’s post, D is for…


So far this month, I’ve been telling you about things that I think will happen (or plausibly could happen) at some point in the distant future.  But today, I’m going to talk about something that’ll happen in the not-so-distant future.  Something that will happen in the very near future, actually.  Later this year, in fact!  In late September or early October of 2022, a NASA space probe named DART will deliberately crash into an asteroid named Dimorphos.

Dimorphos is a relatively small asteroid orbiting a much larger asteroid named Didymos.  Basically, Dimorphos is Didymos’s moon.  These two asteroids will be passing fairly close to Earth later this year.  Now I want to be 100% clear about this: neither Didymos nor Dimorphos are going to collide with our planet.  We are in no danger.  But these asteroids will be coming close enough that we could do a little experiment—an experiment to see just how well we could defend our planet from a dangerous, mass-extinction-causing asteroid, should such an asteroid ever come our way.

DART stands for Double Asteroid Redirection Test.  As you can see in the highly technical diagram below, the plan is for the DART spacecraft to have a head-on collision with Dimorphos.

This head-on collision should cause Dimorphos to lose some orbital momentum, which should alter Dimorphos’s orbit around Didymos.  How different will Dimorphos’s new orbit be?  Hard to say.  The exact angle of impact… the astroid’s mineral composition… the amount of debris produced by the collision… all of these things may factor into what Dimorphos’s new orbit looks like.

Astronomers can do all the computer simulations they like, but until we throw a real life projectile at a real life asteroid, we won’t really know what will happen.  Not with any kind of precision.  Ergo, we need to do this experiment.

Looking once more into the distant future, I believe that humanity is going to spread out across space.  Large numbers of people will eventually be living on the Moon and Mars, as well as on other planets and moons of our Solar System.  But I also believe these humans in the distant future will take good care of the Earth.  Among other things, they will know how to defend Earth from incoming asteroids and comets, so that what happened to the dinosaurs never has to happen again.  And that capability—the capability to keep Earth safe from killer asteroids and comets—begins with a little NASA experiment scheduled to occur later this year.

Want to Learn More?

Here are a few papers that I’ve been reading about the upcoming DART Mission.  This is where I got most of the information for today’s post:

Protect Europa!

Hello, friends!  We’ve reached the end of October, which means we’ve reached the end of Europa month here on Planet Pailly.  We still haven’t determined whether or not Europa is home to alien life, but I hope I’ve persuaded you to take the possibility of life on Europa seriously.

One question that came up a few times this month was whether or not we should send humans to Europa.  The answer, in my opinion, is no.  First off, as we discussed in a previous post, the radiation environment on Europa is crazy dangerous.  We humans would also struggle with the extreme cold and the very low surface gravity.  I’m not saying a colony on Europa is impossible, but there are far safer and easier places we could choose to go.  The neighboring moons of Ganymede and Callisto, for example, would serve as safer and more comfortable bases of operation for humans.

But there’s another reason why colonizing Europa seems like a bad idea to me.  It’s not a science reason.  It’s a legal issue.  There’s an international agreement in place (Article IX of the 1967 Outer Space Treaty) which forbids space agencies like NASA, the E.S.A., or Roscosmos from contaminating other worlds with our Earth germs.  The same agreement also forbids contaminating Earth with germs from other planets.

Some missions are considered riskier than others, contamination-wise.  For example, Article IX doesn’t really apply to NASA’s Parker Solar Probe.  There’s no chance Earth germs will be able to contaminate the Sun (and since the probe will not be returning to Earth, there’s no chance any lifeforms from the Sun could contaminate Earth).  There’s actually a whole risk categorization system in place, with five different categories of risk, and a bunch of sub-categories, too.  Click here if you want to know more details about that.

The important thing for our purposes is that any mission to Europa will involve a very high risk of contamination.  We may not know yet if alien life exists on Europa, but the possibility should be taken seriously.  The people who wrote the Outer Space Treaty made it clear that they’d learned the lessons of history and did not want to repeat the mistakes of the past.  We would not want Earth germs to endanger an alien ecosystem on Europa (nor would we want Europa germs endangering Earth-life).

So for the foreseeable future, I think Europa will be off limits to humans.  Europa might even be declared an interplanetary wilderness preserve, or something like that, and if there’s scientific research to be done on Europa, it can be done remotely from bases on Ganymede or Callisto.

There are easier places in the Solar System for us humans to colonize.  There’s no need for humans to go there.  So unless and until someone shows the contamination risk on Europa is zero, let’s leave Europa alone.


As part of my research for this post, I read the two papers listed below.  If you’re interested in how Earth laws work (or don’t work) in outer space, these papers are worth a look.  Also, if you’re interested in writing Sci-Fi, these papers may get the wheels of your Sci-Fi writer brain turning.

October Is Europa Month Here on Planet Pailly!

Hello, friends!  Let’s talk about aliens!

If we want to find alien life, where should we look?  Well, if money were no object, I’d say we should look anywhere and everywhere we can.  Phosphorous on Venus?  Could be aliens.  Let’s check it out.  Melty zones beneath the surface of Pluto?  Let’s check that out too.  Ariel?  Dione?  Ceres?  Let’s check them all for signs of alien life!

But money is an object.  We simply don’t have the resources to explore all of these places.  Space exploration is expensive.  Space exploration will always be expensive so long as we’re stuck using rocket-based propulsion.  The Tsiolkovsky rocket equation makes it so.

Whenever you’re working within a restrictive budget, you need to think strategically.  With that in mind, astrobiologists (scientists who specialize in the search for alien organisms) have focused their efforts on four worlds within our Solar System.  Their names are Mars, Europa (moon of Jupiter), Enceladus (moon of Saturn), and Titan (another moon of Saturn).

This month, I’m going to take you on a deep dive (no pun intended) into Europa.  In my opinion, of the four worlds I just listed, Europa is the #1 most likely place for alien life to be found.  I don’t mean to denigrate Mars, Enceladus, or Titan.  There are good reasons to think we might find life in those places, too.  But there are also good reasons to think we might not.

  • Mars: Life may have existed on Mars once, long ago.  But then the Martian oceans dried up.  We’re unlikely to find anything there now except, perhaps, fossils.
  • Enceladus: Enceladus’s age is disputed.  She may be only a few hundred million years old, in which case she may be too young to have developed life.
  • Titan: If you want to believe in life on Titan, you have to get a little imaginative about how Titanian biochemistry would work.

Europa doesn’t have those issues.  Unlike Mars, Europa has an ocean of liquid water right now, in modern times.  Unlike Enceladus, Europa’s age is not disputed; she’s definitely old enough for life.  And unlike Titan, Europa doesn’t require us to get imaginative about biochemistry.  The same carbon-based/water-based biochemistry we use here on Earth would work just as well for the Europans.

There are still good reasons to search for aliens on Mars, Enceladus, and Titan.  Finding fossils on Mars would be super exciting!  Enceladus’s age is, as I said, in dispute, with some estimates suggesting she’s very young, but others telling us she’s plenty old.  And while life on Titan would be very different than life on Earth, scientists don’t have to imagine too hard to find plausible ways for Titanian biochemistry to work.

But if I were a gambler, I’d put my money on Europa.  And if I were in charge of NASA’s budget, I’d invest heavily in Europa research and Europa missions.  Europa just seems like the safest bet to me, if we want to find alien life. And in the coming month, I plan to go into more detail about why I feel that way.


If you’re interested in learning more about the Tsiolkovsky Rocket Equation, you may enjoy this article from NASA called “The Tyranny of the Rocket Equation” (because NASA is the American space agency, and anything Americans don’t like is tyranny).

As for astrobiology, I highly recommend All These Worlds Are Yours: The Scientific Search for Alien Life, by Jon Willis.  Willis frames the search for alien life just as I did in this post: alien life could be anywhere, but you only have a limited budget to use to find it.  So how would you spend that money?

Sciency Words: Heartbeat Tone

Hello, friends!  Welcome back to Sciency Words, a special series here on Planet Pailly where we talk about those weird and wonderful terms scientists use.  Today’s Sciency Word is:


Last week, I watched NASA’s live coverage of the Perseverance rover landing on Mars.  Naturally, I had a notepad ready, and I picked up quite a few new scientific terms.  My absolute favorite—the one that brought the biggest smile to my face—was “heartbeat tone.”  I love the idea that Perseverance (a.k.a. Percy, the Mars Rover) has a heartbeat.

As this article from Planetary News describes it, Percy’s heartbeat tone is “similar to a telephone dial tone.”  It’s an ongoing signal just telling us that everything’s okay.  Nothing’s gone wrong, and everything’s still working the way it’s supposed to.

Of course, other NASA spacecraft use heartbeat tones as well.  According to two separate articles from Popular Mechanics, the Curiosity rover on Mars and the Juno space probe orbiting Jupiter also send heartbeat tones back to Earth.  And that article about Juno offers us a little bit of detail about what Juno’s heartbeat actually sounds like: a series of ten-second-long beeps, sort of like very long dashes in Morse code.

Based on my research, it seems like the earliest NASA spacecraft to use heartbeat tones (or rather, the earliest spacecraft to have this heartbeat terminology applied to it) was the New Horizons mission to Pluto, which launched in 2005.  As this article from Spaceflight 101 explains it, New Horizons’ onboard computers monitor for “heartbeat pulses” that are supposed to occur once per second.  If these pulses stop for three minutes or more, backup systems kick in, take over control of the spacecraft, and send an emergency message back to Earth.

So, I could be wrong about this, but I think this “heartbeat pulse” or “heartbeat tone” terminology started with New Horizons.  To be clear: I’m sure spacecraft were sending “all systems normal” signals back to Earth long before the New Horizons mission.  I just think the idea of using “heartbeat” as a conceptual metaphor started with New Horizons.  But again, I could be wrong about that, and if anyone has an example of the term being used prior to New Horizons, I would love to hear about it in the comments below!

P.S.: I recently wrote a post about whether or not planets have genders.  With that in mind, I was amused to note in NASA’s live coverage that everyone kept referring to Perseverance using she/her pronouns.  However, the rover has stated a preference for they/them on Twitter.  So going forward, I will respect the rover’s preferred pronouns.

Is There Life on Earth?

Hello, friends!

Let’s imagine some space aliens are cruising by our Solar System.  They turn their scanners on our planet and see… what?

Among other things, they’d notice that Earth’s landmasses are partially covered with a strange, green-colored substance.  Of course, you and I know what that green substance is.  It’s chlorophyll.  But would those extraterrestrial observers, who have no prior knowledge of our planet, be able to figure that out?  Even if they did, would they realize what chlorophyll is used for?  Maybe.  Probably not, though.

Which brings me to my all-time favorite scientific paper: “A search for life on Earth from the Galileo spacecraft,” by Carl Sagan et al.  I love this paper in part because it’s so clearly and concisely written, with jargon kept to a minimum.  Sagan was, after all, a talented science communicator.  But I also love this paper because its conclusions are so shocking, so eye-opening.

In 1990, NASA’s Galileo spacecraft turned all its high-tech instruments toward Earth and detected… not much, actually.  Galileo did pick up radio broadcasts emanating from the planet’s surface.  Aside from that, though, Galileo’s data offered highly suggestive (but also highly circumstantial) evidence on Earthly life.  The lesson: finding life on other planets is hard.  Even using our very best equipment, it was hard for NASA to detect signs of life right here on Earth!

At least that’s what I got out of reading Sagan’s Galileo experiment paper.  And based on various commentaries I’ve read or heard about this paper, that seems to be the lesson other people got out of it too.  So I was surprised to hear Sagan himself, approximately seven-and-a-half minutes into this interview, saying the exact opposite.

We’ve flown by some sixty worlds.  We claim that we haven’t found life anywhere, and that that is a significant result.  That is, that we would have found life had it been there.  But this has never been calibrated.  We’ve never flown by the Earth with a modern interplanetary spacecraft, all instruments on, and detected life here.  And so Galileo, because of this peculiar gravity assist VEEGA trajectory, permits us to do that.  And as I’ll describe tomorrow, we find life five or six different ways, including intelligent life.  And this then means that the negative results that we find elsewhere are, in fact, significant.

I’ve been puzzled by this for a while now, but I think I’ve finally figured out why Sagan would say this.  It’s politics.

On the one hand, scientists need to understand the challenges they’ll face (including the limitations of their own equipment) in searching for life on other worlds.  That really is, I think, the purpose of the Galileo experiment paper.  On the other hand, it would not do to say on public television, to cantankerous taxpayers and the listening ears of Congress, that NASA spends millions of dollars on space probes that are not even capable of detecting life right here on Earth.

Space exploration is expensive.  And like all expensive types of research, sooner or later the researchers involved have to learn how to play politics.

Sciency Words: Safety Ellipse

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we talk about those wild and crazy words scientists use.  Today’s Sciency Word is:


I don’t know about you, but when I’m trying to dock my shuttle pod with another spaceship, I like to take a few long, leisurely loops around that other spaceship first.  You know, like this:

Spaceships are pretty!  Who wouldn’t want to get a good look at them from every conceivable angle before completing docking maneuvers?  But it turns out that circling round and round a spaceship like this is not just for admiring the view.  It’s also for safety!  As explained in this paper:

A “safety ellipse” is an out-of-plane elliptical periodic relative motion trajectory around the primary spacecraft such that the trajectory never crosses the velocity of the primary.

That clear things up?  No?  Okay, how about a quote from this paper instead:

This paper defines a safe trajectory as an approach path that guarantees collision avoidance in the presence of a class of anomalous system behaviors.

Still confused?  Here’s a short video demonstrating what a safety ellipse (a.k.a. a safe trajectory) looks like:

Basically, if your shuttle pod experiences engine failure or any other major malfunction, flying in a safety ellipse ensures that you will not collide with the ship you were trying to dock with.  At least not for a good, long while.

I first heard about this term the other day while watching the livestream of the SpaceX Dragon capsule approaching and docking with the International Space Station.  Several times, the livestream commentators mentioned that Dragon was utilizing a “24 hour safety ellipse” or “24 hour safe trajectory,” meaning that if anything went wrong, mission control would have at least 24 hours to fix it before Dragon and the I.S.S. collided.

So remember, friends: the next time you’re going to dock with another spacecraft, do that out-of-plane elliptical periodic relative motion thing.  In other words, circle around the other ship a few times before making your final approach to dock.  It’s for safety reasons.

P.S.: It’s also for enjoying the view.  Spaceships are pretty!

Sciency Words: Orthofabric

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we explore the definitions and etymologies of scientific terms.  Today on Sciency Words, we’re talking about:


If you’re planning to spend any amount of time floating around in outer space, you need to dress appropriately.  You’ll need protection against solar and cosmic radiation.  You’ll need protection against extreme temperatures, both extreme cold and extreme heat (direct sunlight in the vacuum of space can make things super hot super quick).  Oh, and there are lots of tiny micrometeoroids whizzing about up there.  You’ll need protection against those too.

Around the same time that the space shuttle program got going, NASA started using a new fabric for the outermost layer of their spacesuits.  That fabric is still used today for spacesuits aboard the International Space Station.  It’s called Orthofabric (sometimes spelled with a hyphen: Ortho-fabric).

Orthofabric is made by a company called Fabric Development Inc., based in Quakertown, PA.  Orthofabric is made using three different synthetic fibers: Gore-Tex, Nomex, and Kevlar.  As reported in several research papers (like this one or this one), Orthofabric consistently holds up well against the harsh conditions found in space.  That’s why NASA keeps using it.

For these Sciency Words posts, I think it’s important to say something about the etymology of the word we’re talking about, but I had an extremely hard time finding any sort of etymology for this one.

The prefix “ortho-” comes from a Greek word meaning righteous, virtuous, or pure (hence the word orthodox).  “Ortho-” can also mean upright or straight (hence the word orthopedic).  But what do either of those meanings have to do with Orthofabric?  The prefix “ortho-” also has a specialized meaning in chemistry, but based on my research, the chemistry sense of “ortho-” didn’t seem relevant to Orthofabric either.

So finally, I picked up the phone, called Fabric Development Inc., and asked.  I was told the name Orthofabric was chosen after some back and forth consultation with NASA.  The name doesn’t mean anything in particular.  It’s just a name.  I guess somebody thought it sounded good.  End of story.

P.S.: NASA’s new Perseverance rover will be searching for life on Mars, but as a little side experiment Perseverance is also carrying a small sample of Orthofabric, along with samples of other commonly used spacesuit materials.  NASA wants to see how well these spacesuit materials hold up in the windy and dusty Martian environment.

Sciency Words: Perseverance

Hello, friends!  Welcome back to Sciency Words, an ongoing series here on Planet Pailly where we talk about science or science-related terms.  Today on Sciency Words, we’re talking about:


Mars rovers are among the most advanced pieces of technology we humans have ever produced.  And by a longstanding tradition dating back to the Sojourner rover in 1997, the official names for NASA’s Mars rovers are chosen by school children.

The Perseverance rover, currently on route to Mars, was named by 7th grader Alex Mather.  He won an essay contest.  Here’s a video of Mather reading his essay, followed by a quick Q and A session with some NASA officials.

You know, after listening to Mather’s essay, I have to agree.  Perseverance is the right name for our newest Mars rover.  It’s even more right of a name now than it was back in March, when the name was announced.

Things are scary here on Earth.  So many people are suffering.  So many people are struggling.  So many lives are being needlessly lost.  But I do believe, as Mather says in his essay, that perseverance is our most important quality as a species.  In the end, humanity will persevere.