Interested in learning more about #Venus—and why @NASA's decision to go back there with the #VERITAS and #DAVINCI+ missions is such a big flippin' deal?
Venus and Earth are the same(ish) size, age, and composition (in roughly the ~same proportions), orbiting the same star.
So, uh... what's going on?
Here's where we come to our two different stories for Venus—and why figuring out which one is correct is *critical* to understanding not only our own world, but Earth-size worlds everywhere.
Scenario 1: Venus was *always* fucked.
In Scenario 1, Venus started life with a magma ocean, and likely a thick, CO₂ atmosphere.
But it was close to the Sun, and couldn't lose heat as fast as it built up.
So Venus, pretty much from the start, entered a "runaway greenhouse effect".
Game over, thanks for playing.
But in Scenario 2... Venus might have been just like Earth.
*If* Venus survived its early childhood, recent models suggest that it might have had oceans, and maybe even plate tectonics.
It's *possible* that, for >3 billion years, there were two blue marbles in the Solar System.
In Scenario 2, Venus enters a runaway greenhouse, but not because of its proximity to the Sun—but from a self-inflicted cause: volcanoes.
Those same models say that several MASSIVE eruptions could have dumped so much CO₂ into the air that the climate simply could not cope.
The temperature rises, the oceans start to evaporate more and more, which dumps more and more water vapor—itself a greenhouse gas—into the atmosphere, which causes the temperature to rise—
You get the picture.
A once Earth-like world starts to die.
And, eventually, that once-blue world loses its surface water entirely, plate tectonics (which requires water) shuts down, but volcanic activity continues... pouring out lava and continuing to thicken the atmosphere with SO₂ and CO₂.
And we end up with the Venus we see today.
One of these models is wrong.
But we don't know which one.
We don't know if what happened to Venus could happen to Earth.
And how the hell can we make sense of Earth-size exoplanets, if we don't know which scenario's the right one?
NASA has not sent a dedicated mission to study Venus since the Magellan radar mission in 1989.
That mission ended in 1994. And we have come up with a LOT of questions since then.
So, these missions being picked is a HUGE deal because it's been 32 years since NASA sent a mission to Venus.
It's *also* a huge deal because, though we hoped for 2 selections from the 4 shortlisted missions, we thought we'd get VERITAS *or* DAVINCI+.
BUT HOLY FUCK WE GOT BOTH.
VERITAS will carry a radar to obtain image and topographic data for Venus that we BADLY need, at resolutions comparable to what we have for Mars.
I cannot begin to emphasise just how important those data will be.
Like, we'll be using those data for *decades* more.
VERITAS will *also* carry an instrument capable of measuring—for the first time from orbit—the chemical composition of rocks across the ENTIRE planet.
Folks, we don't really know what Venus' surface is made of.
VERITAS will help tell us.
"BUT PAUL",
I hear some goddamn Mars sympathiser ask,
"WhY aRe We SeNdInG tWo MiSsIoNs To VeNuS dOn'T bE gReEdY"
The second mission isn't the same. Where VERITAS maps the surface, DAVINCI+ takes a deep dive *into* the atmosphere...
DAVINCI+ (which also has an orbiter, btw) will drop a probe into the hellsphere—and that probe will measure the atmosphere's composition during an hour-long descent to its death.
The measurements it'll take?
They'll tell us whether Venus ever really did have oceans or not.
And there's something extra cool about DAVINCI+...
The probe isn't designed to survive the landing, but it'll come down in one of Venus' enigmatic "tesserae"—an ancient terrain type on the planet about which we have no real goddamn idea.
And it'll take pics the whole way down.
DAVINCI+ will tell us what the atmosphere's made of, and from that the planet's climate history, and will give us our first real glimpse at Venus' ancient terrain.
VERITAS will show us the entire surface as never before, and help us figure out if it's geologically active today.
I want to be clear.
These two missions won't "solve" Venus. No two, or three, or even four missions will do that.
But having both VERITAS and DAVINCI+ exploring different aspects of Venus this decade?
It's going to REVOLUTIONIZE how we understand planets... including our own.
I've skipped a LOT of details and nuance—but I'll be talking about these missions for years to come.
Just know this: in the 1980s, we thought we understood Mars. We were wrong.
We still don't really understand Venus.
But we're going to put that right.
And it'll blow you away.
Oh, one more thing.
Next week, @ESA will announce the mission they're picking for their *own* competition.
Another stunning example of gravitational lensing in deep space revealed by #JWST.
And there is a single Milky Way star in this image.
Everything else is a galaxy.
This view from @NASAWebb @ESA_Webb shows galaxy cluster PLCK G165.7+67.0 (also called G165), an enormous gravitational mass about 3.6 *billion* lightyears away that's so big it's bent the light of yet more distant objects behind it.
@NASAWebb @ESA_Webb In particular, the orangey band at lower-left of the central cluster contains three brighter points of light that are in fact the *same* Type Ia supernova "H0pe", imaged thrice and enabling scientists to gain a better insight into the expansion rate of the Universe.
Friends, a few weeks ago I told you about something called Phantom—the Venus balloon mission concept I've been leading since January.
In July, we successfully flight-tested a subscale prototype of our balloon in the Nevada desert.
Now we've a video of those tests.
Take a look.
This video documents just a tiny bit of the *enormous* amount of work folks have put into developing these balloons—much of that work predating my joining the mission concept team.
Importantly, these tests validate the technologies we hope to propose to NASA for eventual flight.
You might remember, in my recent thread, that we might not even have the chance of proposing our mission concept to NASA in the next competition round.
That's something we're working hard on to fix.
But now, for the first time, we know we can fly a variable-altitude balloon.
NASA's #ParkerSolarProbe was able to image the surface of #Venus from space in a way we didn't think possible before!
Here, we can see the Aphrodite Terra highland *glowing* through the clouds (left), exactly where radar data tell us it should be (right)!
Venus' thick cloud layer obscures the surface from space at visible wavelengths—but there are some "windows" at near-infrared wavelengths where cameras can see through to the surface.
PSP took these images at a wavelength not thought to be able to penetrate the clouds before.
This matters because, unlike Mars, Mercury, the Moon, etc, we can't easily see the Venus surface—we have to use radar.
But if we can "see" the surface in the near infrared, we can start to learn things about what it's made of. And thus we can learn new things about Venus.
A quick 🧵 about the *size* of the #HungaTonga eruption:
Volcanic eruptions are generally assigned a VEI—Volcanic Explosivity Index—value.
This scale is a general indicator of the explosive character of an eruptive event.
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This scale, described by Christopher Newhall and Stephen Self in a 1982 paper, is a general indicator of the explosive character of an eruptive event, and reflects the interplay of an eruption's magnitude, intensity, and energy release rate.
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The VEI rating scale employs a set of criteria including ejecta volume, style of eruption, plume height, and injection of gases into the troposphere and stratosphere.
There's no question that the #Tongaeruption was huge—it absolutely was.
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I need you to know I'm being completely serious here.
We have no idea what's inside Uranus.
We really don't have a clue what's inside this or there other "ice giant", Neptune.
It's possible that there's a rocky interior, perhaps at least as large as Earth. There might be a water–ammonia ocean above that rocky centre, topped with a thick atmosphere.
But we don't know.
Uranus and Neptune are the outer Solar System's Venus -- fascinating, largely unexplained, but to be honest pretty much ignored in the modern era of planetary exploration.
The Solar System is *full* of incredible and fascinating worlds!
Mercury.
Venus.
Earth.
The Moon.
Jupiter.
Saturn.
Uranus and Neptune.
Ceres, Vesta, and the other main asteroid belt bodies.
The myriad other minor bodies scattered across the System.
Every one of them amazing! 🥰
People are pointing out that I forgot somewhere important!
Somewhere that fascinates everyone, that we need to explore more, that holds a special place in our heart.