NASA’s DART

The Dart Impactor (gold) being loaded into the faring of the launch vehicle at Vandenberg Launch Facility

Wow! Have you been following NASA’s DART mission? “DART” is one of those Ghastly-Acronyms-which-Spell-out-the-Project (GASP!) which stands for “Double Asteroid Reflection Test”. Scientists are always discouraged that their jaw-dropping projects conducted in outer space can never garner the same level of attention as inane sports and celebrity folderol–so they give missions these names with futile hopes of grasping the popular imagination. Speaking of whipping up attention, you should immediately google “DART” to see Google’s unprecedented graphic/animation (uh, and all of the information and scientific details about this project, of course).

Anyway, the project’s name aside, DART is a smashing success and something which humankind should have been working on since the dawn of the space age. Ever since we finally understood what caused those craters on the moon (which took longer than you might expect) and the Alvarez hypothesis explained what caused the Cretaceous-Paleogene mass extinction, scientists and engineers have realized that humankind needs a proper planetary defense system to protect us from meteors, bolides, comets, space shards, and whatever cosmic flotsam and jetsam has been drifting around out there waiting to wreck us the same way the poor dinosaurs got creamed.

“Grawwwwwr! Why did we spend so much on stock buybacks and so little on basic science?”

Although some previous asteroid and comet exploration missions have edged towards testing the behaviors of space objects subjected to manmade impacts and forces, the DART mission was designed specifically for the purpose of finding out about such things. Back in November of 2021 NASA launched a 610 kilogram impactor spacecraft to crash into Dimorphos (a tiny asteroid which orbits the larger asteroid Didymos). On September 26 (2022) the impactor crashed into Dimorphos as the Italian mini-satellite LICIACube looked on (as did many of our best telescopes).

Here is a NASA schematic which explains the mission (and its hypothesized outcome) far better than I could.

Of course in the grand scheme of things 610 kilograms is not very much mass–although a 610 kilogram (1340 lb) linebacker smashing into you would probably wreck your day–especially if he was running 6.6 kilometers per second (15,000 miles per hour) which was the closing velocity of the projectile and Dimorphos. Indeed, the Hubble and Webb space observatories were both keeping an eye on the collision and the results were pretty explosive.

We will await the exact numbers (scientists speculate that such an impact should release 20-30 gigajoules of energy–approximately equivalent to detonating 6 or 7 tons of TNT). Also, an EU spaceship named Hera is being dispatched to survey the results in 2026 (so more to follow). For now though, I am already breathing easier knowing that someone is finally working on this problem. Now we just need to work on the 8 billion other problems which are affecting Earth and casting a pall over humankind’s glorious future,

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An Unexpected Portrait of the Neptune System

We knew that, if the Webb telescope could make it to the L₂ Lagrange Point in one piece and deploy properly, this would be an exciting season for astronomers–but, even so, the parade of stunning new images from outer space are marvelous and demand comment. Today’s treasure is a picture of Planet Neptune and its moons as imaged by the near-infrared camera on Webb. The ice giant Neptune is made of strange cold things with a great pall of methane gas over them. Methane gas is very opaque to infrared light (which it absorbs) and so the planet looks like a frosty, haunted bowling ball with glass rings.

Ever since Pluto got demoted to “dwarf planet”, Neptune is the outermost world of our solar system. Yet the great gas giants…or even the trans-Neptunian objects like Eris and Haumea get all of the attention. No space craft has even visited Neptune since Voyage II rolled by in 1989 (the first and last time a probe entered the Neptune system).

Aside from the spectral rings, the image shows some bright sparks in a line along Neptune’s Tropic of Capricorn (which is not called that, but you get the idea). These bright spots are caused by high altitude methane clouds which are made of methane ice (which reflects infrared light better than methane gas does).

The full Webb photo has a striking focal point! Pulling back we see that Neptune’s largest and strangest moon Triton outshines the giant world it orbits. This is because Triton (which is named for the Greco-Roman deity Neptune’s merman super-son) is covered in a sheet of frozen nitrogen which reflects 70% of the sunlight which strikes it–so Triton glows like an aquamarine star in this photo. Ultimately Triton might well turn out to be be more interesting than Neptune: it is the only large moon in the solar system with a retrograde orbit (an orbit opposite of the planet’s rotation). Such an unusual orbit suggests that the moon was a little world captured by the ice giant long ago.

Triton is larger than Pluto and is one of five moons in the solar system known to be geologically active (the others being Io, Europa, Titan, and Enceladus). Voyager II spotted geysers of nitrogen gas venting from the moon. Clearly cryovolcanic activity is taking place below the strange patchwork of old ice (as explained in this confusing yet compelling map/diagram) and lakes of liquid water may exist below the moon’s crust.

I am going to keep staring at images of our strange far-off neighbor world, but I can’t wait to see what Webb photographs next!

Webb’s First Deep Field

Hey everybody! Sorry I went awol for a little sabbatical from writing. It is summer plus I felt burned out after the last two (or 20) years, and none of my blogging pleasure centers were registering any joy. However today there is something to be quite joyous about: the President of the United States released the first deep field image from the James Webb Space telescope, a colossal near-infrared eye in the sky, which is now unfurled, debugged, and fully operational at Earth’s second LeGrange point! Huzzah!

Courtesy NASA Webb Space Telescope

And what a picture it is. It is so good and so spectacular that it almost looks like background art from a disco album rather than a colossal galaxy-studded expanse of outer space as it existed billions of years ago. The image is a composite of multiple scans taken with the space telescope’s Near-Infrared camera over a 12.5 hour window (the world famous ultra deep field photo from Hubble which rocked the world back in 2004 required closer to 12 days of scope time and did not peer early so deeply into the universe).

The Webb image shows the galaxy cluster SMACS 0723 which is 4.6 billion light years away. Because this galaxy cluster is (or was?) so massive, it acts as a gravitational lens and much more distant galaxies can be glimpsed in the curvy fisheye at the center of this image. I am no galactic astronomy expert (here are some vague pointers about what the color means from an earlier post), but the beauty and grandeur of the image is evident to even the rankest layman…and this is the first real image. There are going to be lots and lots of additional pictures coming in of every conceivable sight out there in the universe and we are going to be blown away by what we see. I can hardly wait for more!