Radiation on Europa: How Quickly Would It Kill You?

Hello, friends!  If you happen to have any radiation protection clothing lying around—like those lead aprons they give you for X-rays at the dentist—I recommend putting it on now before you read any further.  In today’s post, we’ll be exploring the radiation environment of Europa.

Europa is often listed as one of the top four places in the Solar System where we might find alien life.  That makes exploring Europa a top priority for NASA and other space agencies.  Unfortunately, Europa is one of the moons of Jupiter, with an orbit that puts Europa deep inside Jupiter’s radiation belts.

Radiation is going to be a problem wherever you go in space, but the radiation belts around Jupiter are extra scary. If you were to spend a few days on the surface of the Moon or Mars without any sort of radiation protection gear, you’d end up with a significantly higher risk of developing cancer at some point later in life.  If you spent a similar amount of time on the surface of Europa without radiation protection, you wouldn’t live long enough to worry about cancer.  Radiation sickness would kill you in a matter of days—maybe a matter of weeks, if you’re “lucky.”

– NASA’s Juno space probe flying through radiation near Jupiter.

Even robotic spacecraft have a tough time dealing with Jupiter’s radiation belts.  The Juno mission, currently orbiting Jupiter, has all its mission critical electronics sealed up inside what NASA calls a radiation vault.  It’s basically a big, heavy box with thick walls made of titanium.  The radiation vault cannot block all of the radiation, but it blocks enough of it that Juno should survive long enough to finish its mission.

NASA’s upcoming Europa Clipper mission, which will take an even closer look at Europa, will be equipped with a similar radiation vault.

Before we end today’s post, some of you may be wondering what all this radiation means for potential alien organisms living on Europa.  Well, it probably wouldn’t affect them much, if at all.  The aliens (if they exist) would be swimming around in Europa’s subsurface ocean, beneath several kilometers worth of water ice.  And large quantities of water happen to be one of the very best radiation shields nature can provide.


  • “Colonization of Europa” from Wikipedia.  Yeah, it’s a Wikipedia article, but if you’re interested in what it would take to put human beings on the surface of Europa, this article is a pretty good place to start.
  • “Juno Armored Up to Go to Jupiter” from nasa.gov.  This is a press release from 2010, when the Juno spacecraft was still under construction.  It describes, in plain English, what Juno’s radiation vault is and why Juno needs it so badly.
  • “Spent Fuel Pool” from What If?  For those of you who didn’t know about water’s incredible radiation blocking powers, this is an amusing look at water’s incredible radiation blocking powers.

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.

Europa’s Cold Spot

I still have a ton of research reading to catch up on from 2018.  This weekend, I read a paper about Europa.  I wasn’t sure at first why this was on my to-be-read list, but by the end I knew why this one had caught my attention.

Europa is one of the icy moons of Jupiter.  It’s often listed as one of the most likely places in the Solar System where we might find alien life.  That’s because there’s evidence of a vast ocean of liquid water sloshing around beneath Europa’s icy crust.

Maybe someday we’ll be able to drop a little robo-submarine into that ocean and see if anything’s swimming around down there. But in the meantime, we’re really only able to explore Europa’s surface.  And as you can see in the highly technical diagram below, no matter where you go on Europa’s surface, it’s cold.  But in one specific region, Europa gets really cold.

Or at least, that one region appears to be extra cold.  This is a case where it’s important to understand how we get our data. We’re really measuring Europa’s thermal emissions, the amount of heat that gets radiated out into space. So that cold spot may represent one of two things:

  • Either that region absorbs less sunlight than the rest of Europa, and so it never heats up in the first place…
  • Or that region does a better job trapping the heat it absorbs from the sun, and so we detect less heat escaping back into space.

Either way, something weird is happening. Unfortunately, our previous missions to the Jupiter system did not provide us any useful photos of that one specific spot on Europa’s surface.  Our current Juptier mission, Juno, is unable to approach Europa at all, so that’s no help.

So we can’t match this anomalous cold spot to a visible surface feature.  However, the authors of the paper I read did suggest that this could be a sign of recent geological activity—the formation of chaos terrain, perhaps.

And if that’s true, we might (might!) find the waters of Europa’s subsurface ocean seeping up to the moon’s surface.  Maybe there’s fresh organic material seeping up onto the surface too.  Maybe.


Could be worth checking out, though.  Don’t you think?