Sciency Words: Biogenic (Alien Eyes on Earth, Part 5)

June 2, 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:

BIOGENIC

A passing alien spacecraft has been observing our little, blue planet for two weeks now, and it’s time they reported their findings back to their homeworld. One word—one scientific term—will feature prominently in their report: biogenic.

Actually, it’ll be the word xygjaflubozux, but that roughly translates into English as biogenic. It’s an adjective meaning “generated by biological processes.”

It’s difficult to impossible to directly detect life forms on a distant planet, so instead good astro-scientists go looking for chemicals that may have biogenic origins.

In the case of Earth, the aliens report they’ve detected an alarming amount of oxygen in the atmosphere. Oxygen is such a highly reactive chemical that it’s hard to imagine how it could persist in a planet’s atmosphere over long periods of time, unless….

Then there’s methane (which we never talked about in this series… oops). The presence of methane is even harder to explain, because methane reacts so readily with oxygen. All that methane should oxidize away within fifty years, unless….

Could it be biogenic oxygen? Biogenic methane? What about some of the other strange chemicals in Earth’s atmosphere, like nitrous oxide? Could there be biological processes at work constantly replenishing these chemicals in Earth’s atmosphere? These questions will be debated among the alien scientific community for many standard cycles to come.

The only unambiguous evidence of life on Earth, from the aliens’ perspective, were those radio signals coming from the planet’s surface. In a sense, you might say these signals have a biological origin, though I doubt human astro-scientists would describe them as biogenic radio emissions. But maybe the word xugjaflubozux has a slightly broader flavor of meaning and could still apply (how should I know? I don’t speak alien!).

This is the final post for my “Alien Eyes on Earth” series. The aliens have to move on and explore other star systems, but something tells me they’ll be back.

Today’s post was inspired by a 1993 paper by Carl Sagan and others. Sagan and his colleagues wanted to know which of Earth’s features can be observed by a passing spacecraft and, perhaps more interestingly, which features cannot.


Alien Eyes on Earth, Part 4

June 1, 2017

Right now, as you read this, our world is being watched keenly and closely by a nearby alien spacecraft. So far the aliens have only observed circumstantial evidence of life: water, oxygen, and a mysterious light-absorbing chemical (chlorophyll). But the aliens are about to detect something that will prove conclusively not only that there’s life on Earth but that there is intelligent life.

Okay, the content of Earth’s radio broadcasts might not seem all that intelligent, but the existence of such broadcasts is clear, unambiguous evidence of a technologically advanced civilization of some kind.

First off, these radio signals are being affected by Earth’s ionosphere in a particularly telling way. During the day, the ionosphere becomes energized by solar radiation, effectively blocking the planet’s radio emissions from escaping into space. But at night, the ionosphere calms down and allows more radio signals through. Because the aliens detect most of the radio emissions from the night side rather than the day side, it would seem clear to them that the signals originate on the planet’s surface, rather than sources near or directly behind the planet.

Secondly, the radio emissions remain stable at constant frequencies over the course of many hours. Naturally occurring radio emissions would tend to drift significantly from one frequency to another over that time period. This strongly suggests an artificial source.

And thirdly, these signals exhibit “pulse-like amplitude modulation”—in other words, the signals appear to be modulated in such a way as to contain bits of information. I imagine this would present something of a double challenge for the aliens: first the technical challenge of decoding the signals, and then the linguistic challenge of interpreting our language—or rather, our many languages.

Whether or not the aliens could make any sense out of these radio signals, this sort of pulsed amplitude modulation is never observed with naturally occurring radio sources. The only reasonable hypothesis is that there is intelligent life on the planet’s surface.

Tomorrow, in the final post for this “Alien Eyes on Earth” series, the aliens will report their findings back to their home planet, and there’s one word—one particular scientific term—that will feature prominently in that report.

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Today’s post was inspired by a 1993 paper by Carl Sagan and others. Sagan and his colleagues wanted to know which of Earth’s features can be observed by a passing spacecraft and, perhaps more interestingly, which features cannot.

P.S.: Of course the aliens would pick up more than just pop music. They’d be able to hear our news, educational programming, personal cell phone calls, coded military transmissions, et cetera, et cetera… but something tells me that music in particular would draw their interest. The special combination of mathematics and aesthetics is, in my opinion, one of the strongest indicators of intelligent life.

 


Jupiter’s All Warm and Fuzzy Inside

May 30, 2017

Don’t let Jupiter’s stormy personality fool you. He’s all warm and fuzzy on the inside.

I have a couple more “Alien Eyes on Earth” posts on the way, but last week one of my favorite space missions was in the news: the Juno mission to Jupiter.

Now I have to confess I haven’t done a whole lot of research on what Juno’s found. I take it some of the highlights are:

  • We got a cool picture of Jupiter’s rings with the constellation Orion in the background.
  • Those cyclones clustered around Jupiter’s poles—those are still weird.
  • It sounds like something freaky is happening with Jupiter’s auroras. I’m planning to do a separate post on that in the near future.

But the thing that really grabbed my attention was this: Jupiter’s core is being described as “fuzzy.” I’m not sure how to visualize that, but it’s also being described as “partially dissolved,” which makes a little more sense to me.

We know about this because Juno is gravity mapping the planet—using highly precise measurements of Jupiter’s gravitational field to determine how mass is distributed in the planet’s interior.

We also know about it thanks to Juno’s magnetometer. Planetary magnetic fields are generated by an internal dynamo effect, the result of all that pressurized liquid metal swirling and churning around a planet’s core. But according to Juno’s magnetometer, it seems Jupiter’s magnetic field is not what we expected, which suggests… what? Multiple dynamo effects? A big dynamo in the middle with smaller dynamos surrounding it?

Again, I haven’t done any proper research about this. Not yet. But I had a thought that I wanted to throw out there: we never figured out why Neptune’s magnetic field is so out of whack.

So now I’m wondering if there could be a connection there. Could weird, confusing, complicated magnetic fields just be a common feature of gas giants?

Also, the Sun has a wildly complex tangle of magnetic field lines around it. Might there be a relationship between the weird magnetic fields of gas giant and the weirder magnetic fields of stars?

I don’t have any answers. I’m just speculating after all the Juno news last week. It’ll be interesting to see what Juno tells us next.

On Thursday, we’ll get back to those aliens studying Earth from a distance.

Links

Jupiter Surprises in Its Closeup from Science Friday.

Jupiter Data from Juno Probe Surprises Scientists from Solar System Digest.

Jupiter Surprises in First Treasure Trove of Data from NASA’s Juno Mission from Spaceflight Now.


Sciency Words: Photosynthesis (Alien Eyes on Earth, Part 3)

May 26, 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:

PHOTOSYNTHESIS

This post is mainly for my extraterrestrial readers, especially you extraterrestrials who are observing Earth from a distance and are a little puzzled by what you’re seeing.

By now, you’re aware of Earth’s active water cycle, and you’ve observed an alarming amount of oxygen in Earth’s atmosphere. You may have also noticed there’s a strange chemical spread across Earth’s landmasses, a chemical that absorbs red light.

This chemical also absorbs blue light, but due to an atmospheric scattering effect, the blue absorption signature might not be easy for you to see. Also, there’s more of this hard-to-identify chemical in Earth’s oceans, but between the atmospheric scattering of blue light and water’s ability to absorb red, you probably can’t detect it.

I realize you aliens must be pretty advanced. I mean, you’ve developed interstellar travel, after all. Even so, I bet you’re struggling to identify this strange chemical substance. Let me help you out: it’s a weird, complicated molecule we humans call chlorophyll, and it’s used in a biochemical process we call photosynthesis.

Photosynthesis comes from two Greek words: photo, meaning light, and synthesis, meaning synthesis.

Here on Earth, photosynthetic life forms like plants, algae, and cyanobacteria use chlorophyll to absorb sunlight (specifically the red and blue wavelengths). This light energy is then used for a sort of carefully controlled photolysis of water and carbon dioxide molecules, which are then recombined to make carbohydrates.

Please note: there are alternative versions of photosynthesis here on Earth that do not require chlorophyll. It’s just that these alternatives aren’t very popular. Haven’t been for over two billion years. This despite the fact that chlorophyll-based photosynthesis produces an extremely hazardous byproduct: oxygen. But hey, at least now you know where Earth’s mysterious oxygen atmosphere comes from!

You probably have something like photosynthesis back on your home planet, but I imagine the details must be different. Some other chemical probably does the job chlorophyll does here on Earth. Whatever your planet’s photosynthetic chemical is, I bet we humans would have a really hard time identifying it… just as you guys were struggling to identify Earth’s chlorophyll.

* * *

Today’s post was inspired by a 1993 paper by Carl Sagan and others. Sagan and his colleagues wanted to know which of Earth’s features can be observed by a passing spacecraft and, perhaps more interestingly, which features cannot.


Alien Eyes on Earth, Part 2

May 25, 2017

If an alien spaceship were passing by, there are several things the aliens would notice about Earth, even from a distance. Water, for one thing. And not just any old water, but water in solid, liquid, and gaseous phases. And if that weren’t enough to grab the aliens’ attention, a spectrographic analysis of the atmosphere would reveal another big surprise: oxygen. Alarmingly high quantities of oxygen.

We humans are used to thinking of oxygen as a good thing, something beneficial to life. From an alien perspective, that may not be so. Imagine if I told you about a planet with a 20% chlorine atmosphere. Would you want to go there? Probably not. Chlorine is a highly reactive, extremely toxic chemical. It’s an oxidizer. One of the strongest oxidizers on the periodic table.

But as you could probably guess from the name, oxygen is also a really strong oxidizer—almost as strong as chlorine. We humans have evolved in an oxygen-rich environment. We’re used to it, and we’ve adapted to it so well that oxygen has become a benefit to us rather than a liability.

To extraterrestrials, however, a 20% oxygen atmosphere could be as frightening as a 20% chlorine atmosphere would be to us.

So where does all that oxygen come from? The aliens already know about Earth’s water, so they might speculate about water molecules being broken apart by UV radiation from the Sun. This process, known as photolysis, would turn water (H2O) into atomic hydrogen and atomic oxygen, which could then recombine to make molecular hydrogen (H2) and molecular oxygen (O2). Light-weight hydrogen molecules would then escape to space and be swept off by the solar wind, leaving the heavier oxygen molecules behind.

That might account for some of Earth’s oxygen, but Earth has a lot of oxygen. A lot more than can be explained by photolysis alone. So how can there be so much oxygen? What keeps all that highly reactive oxygen from reacting itself away… unless something is constantly replenishing Earth’s oxygen supply?

These aliens observing our planet are good scientists, so they won’t jump to conclusions too quickly. It’s possible, the aliens might say to each other, that all this oxygen is being generated by biological activity. But they can’t know that for sure. Not yet.

Tomorrow on Sciency Words, we’ll look at a scientific term that you have almost certainly heard of before, but that the aliens maybe haven’t.

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Today’s post was inspired by a 1993 paper by Carl Sagan and others. Sagan and his colleagues wanted to know which of Earth’s features can be observed by a passing spacecraft and, perhaps more interestingly, which features cannot.


Alien Eyes on Earth, Part 1

May 23, 2017

Aliens are naturally curious about Earth, once they notice it’s there. Earth is covered in water. That by itself isn’t so unusual, but even from a great distance it’s obvious there’s something special about Earth’s water.

Hydrogen and oxygen are the #1 and #3 most common elements in the universe, respectively; therefore, it shouldn’t surprise anyone that H2O, the simplest hydrogen/oxygen compound, is abundant throughout the cosmos.

In a gaseous form, water is often present in the atmospheres of gas giants. Solid water can be found on many asteroids and comets, as well as on icy worlds like Pluto, Titan, or Europa. Liquid water sometimes exists beneath the surfaces of these icy worlds, and it’s sometimes found on rocky worlds like Mars, typically with salt or other impurities mixed in to help lower its freezing point.

But any passing spaceship observing Earth would notice evidence not just of water, not just of liquid water, but clear evidence of water in all three phases.

  • Gaseous water: the characteristic absorption lines of water vapor can be detected in a spectrographic analysis of Earth’s atmosphere.
  • Solid water: highly reflective polar regions indicate the presence of ice.
  • Liquid water: and then there are specular reflections—glints of sunlight reflecting off very smooth surfaces, surfaces so smooth that they almost certainly must be liquid.

It would be one thing to have liquid water sitting stagnant on the planet’s surface, but Earth’s water appears (even from a distance) to be cycling through multiple phase transitions. Passing aliens might not know what that means, but it’s certainly strange enough to make them curious about Earth. Perhaps curious enough to come take a closer look.

* * *

Today’s post was inspired by a 1993 paper by Carl Sagan and others. Sagan and his colleagues wanted to know which of Earth’s features can be observed by a passing spacecraft and, perhaps more interestingly, which features cannot.


Sciency Words: Abstract

May 19, 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:

ABSTRACT

Abstract is kind of an abstract word. It can mean a lot of things to a lot of people. Among those many meanings, “to abstract” as a verb can mean to take specific information and turn it into more generalized—or rather, more abstract knowledge.

I believe this specific to generalization idea is behind the usage of abstract in scientific papers (as well as other kinds of academic literature). An abstract is the first section of a scientific paper. It takes all the specific information presented in the paper and generalizes it into a one-paragraph summary.

Icarus, a prestigious journal of planetary science, advises authors to include three things in their abstracts:

  • The purpose of their research
  • The principle results of their research
  • The major (i.e., generalized) conclusions we might draw from the research

Icarus also says: “An abstract is often presented separately from the article, so it must be able to stand alone.”

Some of you may have wondered why I didn’t mention abstracts in my recent post on how to read a scientific paper. That was an oversight on my part, but there’s a reason for that oversight. I think of abstracts as sort of like the back covers of books. By that I mean I read abstracts to figure out which papers might be worth reading in full.

But once I’ve found a paper I want to read, I don’t pay much further attention to the abstract. Why? Because like the back covers of books, abstracts really aren’t part of the “story” scientific papers are trying to tell. Also, I’ve been warned that abstracts can be oversimplified or misleading.

I recently found this article published by the Indian Journal of Psychiatry. It’s titled “How to write a good abstract for a scientific publication or conference presentation.” In the abstract of this article on abstracts, it says:

Well, that’s what it should have said. What it actually says is this:

Abstracts of scientific papers are sometimes poorly written, often lack important information, and occasionally convey a biased picture.

The article goes on to offer guidance, especially for younger researchers, on how to improve their abstracts. “Misleading readers,” the paper warns in its conclusions section, “could harm the cause of science […].”

Personally, I don’t hold it against scientists if their abstracts aren’t the best. Condensing all your research into one paragraph can’t be easy. The lesson here for people like me who are trying to read this stuff is to take abstracts with a grain of salt—just like the back covers of books.

Okay, next week we’ll stop talking about scientific papers and instead go visit a strange planet. Easily the strangest planet in the Solar System, perhaps in the whole universe. I’m not sure if you’ve heard of it. It’s called Earth.