Things have quietened enough that I'm going to share my thoughts about the detection of #phosphine on #Venus announced yesterday.

In short: this is a BIG fucking deal. And here's why:

(a 🧵)
Phosphine (PH₃) is a fairly rare gas. It forms in giant planets, like #Jupiter, because of the extreme conditions inside them (and because of their hydrogen-rich atmospheres). Neither condition applies to Venus.

PH₃ is also produced by biological activity.
As a result, it's thought to be a useful thing to look for in the atmospheres of #exoplanets that might be habitable.

But nobody expected to find it in the atmosphere of Venus—a world the team led by Prof. Greaves (@jgreaves6) used to test their detection methods.
So what the hell's making the PH₃ detected in Venus' atmosphere?

The atmosphere is *extremely* arid and *unbelievably* acidic, but it's also at (basically) room temperature and pressure. So as things go, it's a lot more habitable than anywhere else on Venus.
In fact, as far as 1961 Carl Sagan (who helped found @exploreplanets) discussed the prospect of life in the clouds of Venus—a message many folks, including @DrFunkySpoon, have also long been sharing with the planetary community and the public.
So... maybe it is life. Wouldn't that be WILD?!

But it probably isn't. There's every chance that some unknown chemical pathway exists to make PH₃ in the Venus atmosphere—assuming the detection is real in the first place. (That's why follow-up detections are *so* important.)
Other geological, abiotic—non-living—processes such as lightning and volcanic activity can make phosphine. And (in my opinion!) Venus is *definitely* volcanic (and is probably erupting right now).
And to the credit of the team reporting this discovery in @NatureAstronomy, they have done *lots* of work trying to figure out what process(es) could explain this detection.

So, to be clear: we do NOT have evidence of life at Venus.

We only have an chemical in the atmosphere.
So what next?

We keep thinking about what explains this detection. We make sure the PH₃ detection is real. We do lab work, computer modelling, everything we can think of.

But here's the thing: we *cannot* resolve this question from Earth.

We MUST go back to #Venus.
And not just because of the phosphine—although we need to try to detect it from orbit, and measure it *from inside* the atmosphere.

But it's possible that Venus was once like Earth is today. It may have had oceans. It may have been habitable. Was it *inhabited*? We don't know.
But the reason this new paper is such a big deal is this:

We can now add Venus as a *potentially* habitable environment in the Solar System—joining Mars, Titan, Enceladus, and numerous other promising worlds.

This detection might turn out to be nothing.

But we should find out.
OK, that's it, that's the thread.

I will *for sure* be talking about Venus again soon. But for now, here's the discovery paper by Greaves et al.—and keep looking up!

nature.com/articles/s4155…

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More from @ThePlanetaryGuy

18 Sep
OK, buckle up, kiddos—here's a 🧵 on our new Geology paper about the enigmatic tesserae on #Venus, and what our new results mean for our understanding of the Hell Planet

Here we go!
First off: what *are* the tesserae (sing. "tessera")?

In short: dunno! Ha.

The longer answer is that they're very heavily tectonically deformed rocks, and where they're found they're the oldest things around: everything else is on top of them.

Here's what they look like:
Lots of work has focused on the tesserae since they were discovered in the 1980s (and named by Russian scientists for parquet flooring!).

We've found lines in several tessera units that curve in such a way that they seem to follow topography. And that's a bit... unexpected.
Read 16 tweets
18 May
At 8:32 am Pacific time, May 18, 1980, it happened.

#MountStHelens exploded, producing the largest landslide ever recorded, sending a tower of rock and ash 19 km into the stratosphere, and killing 57.

I've added the Empire State Building to this image for scale.

A thread:
A shallow earthquake caused the entire northern flank of the volcano to slide. The reduced pressure allowed a huge "cryptodome" of hot, pressurised magma inside the volcano to explode—creating a lateral blast that flattened trees for tens of kilometres.
The eruption blasted fragments of volcanic rock and glass, powered by superheated gases, into a huge column (a Plinian eruption) that reached 19 km into the atmosphere; ash blanketed towns 400 km, and some even landed in the Great Plains, 1,500 km away.
Read 8 tweets
8 May
Yesterday, @geo_spatialist posted this *gorgeous* rendering of a geological map of #Ireland from 1878.

Because I'm procrastinating, here's a short thread on the geology of some of the locales around Ireland, as shown by this map

(1/n)
First up: the Wicklow Mountains (white box on map to the right).

These mountains are a) actually not really mountains at all (just big hills), and b) exposed granite intrusions that were pushed up when an ancient ocean called Iapetus closed up ~420 Myr ago (plus or minus)

(2/n)
Next: the Giant's Causeway in Antrim (upper right)!

This incredible landscape comprises basaltic lava flows that were erupted when the North Atlantic unzipped, around 60-ish Myr ago. The polygonal blocks of lava formed as the molten rock cooled and contracted!

(3/n)
Read 6 tweets
12 Apr
As people are tucking into Easter eggs today, here's a list of some of the *absolute worst* substitutes for chocolate eggs that #geology can offer you. Consider yourself warned.

A THREAD

(1/n)
Type: onion-skinned weathering of massive rocks (including sandstones and granites).

How: formed by weathering along spheroidal fracture planes within the rock mass

Why is bad: it's rock, so will break your teeth, and doesn't at all taste like chocolate

(2/n)
Type: concretions within sedimentary rock (often sandstones)

How: formed by precipitation of minerals around a central mass within sedimentary rock or soil

Why is bad: it's also rock, so will break your teeth, and doesn't at all taste like chocolate either

(3/n)
Read 7 tweets
13 Feb
And the shortlist for #AmericasNextDiscoveryMission has been announced!

@NASA has picked four missions for detailed, 9-month studies under the Discovery-class cost cap; one or two mission finalists will be actually selected for flight around the end of the year.

Read on!

(1/n)
The first is DAVINCI+ (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging Plus), which is a mission to take detailed chemical measurements as it plunges through the Venus atmosphere!

(2/n)
Next is Io Volcano Observer (IVO), which will visit (as the name suggests) #Io, the super-volcanically active moon of #Jupiter!

(3/n)
Read 7 tweets
4 Oct 19
Day 3 of the #VeneraD workshop!

And we're pivoting away from landing sites now and turning to cloud habitability - with the first talk given by Michael Way, about possible conditions on early #Venus!
The next talk is from Shawn Domagal-Goldman, who's describing (remotely, from the US!) how #Venus offers us a useful natural laboratory to understand planetary habitability in general

#VeneraD
Up next: Sanjay Limaye is talking about the still-unknown absorbers of sunlight in the #Venus atmosphere - and the tantalizing possibility that there could be *microbes* in that atmosphere...

#VeneraD
Read 8 tweets

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