Controversy (9/29/22)

Good afternoon, and happy Thursday! This week has been jam-packed with groundbreaking moments in space science, and I can’t wait to dive in. 

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Avenging the Dinosaurs

On Monday, a representative from Planet Earth attempted to change the motion of a celestial object for the first time. NASA’s Double Asteroid Redirection Test (DART) spacecraft crashed head-on into Dimorphos, a football-field-sized asteroid orbiting the larger rock Didymos about seven million miles from home. 

There was a decent amount of uncertainty before the collision as to how much DART would be able to alter Dimorphos’ orbit. This uncertainty came, in part, from how little we knew about the structure of the asteroid—a smooth, solid rock would cause a more elastic collision, while a loose pile of rubble would likely absorb more of the impact in a less predictable way.

Here’s what we know so far:

• DART performed pretty much exactly as planned, striking Dimorphos a mere ~17 m from its target impact site (a bullseye on a cosmic scale).

• The impact kicked up a major cloud of dust, which is now obscuring amateur astronomers’ views of the system.

• Smashing spacecraft into asteroids is awesome ☄️

The DART team at NASA is reviewing the images and data sent home from the spacecraft, as well as additional imagery from the auxiliary camera LICIACube and ground telescopes. The team will continue reviewing that data for the next two months. 

We’ll hopefully know soon how much the impact changed Dimorphos’ orbit around Didymos (and whether crashing a spacecraft into a future oncoming asteroid could be an effective method of planetary defense).

Water on Mars—or not

Whether or not there is water beneath the south polar ice cap on Mars has become somewhat of a Schrödinger's cat for planetary scientists. Radar data reveals bright reflections beneath a thick layer of polar ice that on Earth would usually indicate the presence of liquid water. On Mars, though, many scientists believe that the environment would be far too cold for liquid water to exist.

A group of researchers from Cornell analyzed this contentious radar data and came to the conclusion that these bright sub-ice cap reflections may have been caused not by water, but by stratified geological layers. 

In a lab setting, the researchers tested combinations of materials—atmosphere, water ice, carbon dioxide ice, and basalt—in various arrangements and layers to see if they could simulate the same bright reflections found in the readings on Mars. By layering a sheet of dusty ice between two layers of CO2 ice, the team recorded reflections that appeared as bright on radar as the original readings from the Red Planet.

On the other hand, another study published this afternoon in the same journal, Nature Astronomy, used an alternate data gathering method that provides evidence the bright reflections are, in fact, caused by liquid water. This study used altimeter data to observe the shape of the top layer of ice, and found that those measurements are consistent with what you’d expect from liquid water affecting the ice above.

Neither study claims to know for certain whether there is water underneath the ice. If there is, though, that most likely means that Mars is still geothermically active and provides enough heat to keep that liquid from freezing.

The debate continues…

A Peek at Europa

Europa, the icy ocean moon of Jupiter, has long fascinated planetary scientists as a potential host for life beneath its thick surface. In the late 90s, NASA’s Galileo spacecraft made multiple flybys of the distant moon. In 2000, it made its final approach, taking photos from as close as 218 miles of the moon’s surface.

This morning, after more than two decades of absence, another spacecraft made a close approach to Europa.

NASA launched Juno in 2011 as its great return to the king of planets. The mission arrived at Jupiter in 2016, and since then, it’s been the lone spacecraft surveying the planet. The spacecraft has unveiled new data about Jupiter’s atmosphere and weather patterns. The photos snapped by the spacecraft are the most detailed we have. 

After six years observing Jupiter itself—sprinkled in with a few flybys of Ganymede, another moon—Juno finally made a close approach of Europa. The craft drew within 222 miles of the surface, taking images and data that will be revealed once analyzed by NASA.

Along with snapping the first shots of Europa since 2000, Juno is also taking science measurements. The spacecraft is probing for plasma trailing behind the moon in its orbit, aiming to understand how it’s interacting with Jupiter’s magnetosphere. It’s also using an onboard magnetometer and radio wave experiment to suss out details on the moon’s internal structure.

NASA is planning another mission, Europa Clipper, that will be dedicated to the icy ocean moon. Data from Juno’s flyby will be used to inform Europa Clipper’s targets.

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Other News from the Cosmos

• SOFIA, aka the Stratospheric Observatory For Infrared Astronomy, flew for the last time yesterday evening. The modified Boeing 747 has put in 15 years of work identifying faraway galaxies.

• Satellogic won a contract through the Green+ Jurisdictional Programme to monitor the Earth's protected forests through 2025.

• A protogalaxy in the constellation Sagittarius containing ~0.2% of the Milky Way’s stellar mass may have been the galaxy’s original center more than 12.5 billion years ago, a new study from the Max Planck Institute found.

• Jupiter recently experienced a “heat wave,” reaching temperatures of 700°C across a region more than 80,000 miles wide—10x the diameter of the Earth.

• Mysterious ripples across the outer disc of the Milky Way were likely caused by collisions with a dwarf galaxy, data from the Gaia spacecraft suggest.

• The first data analysis from asteroid Ryugu has been released. Researchers found carbon, nitrogen, and oxygen in the asteroid sample, and also found that the ratio of oxygen to silicon in the sample was different from other asteroids studied on Earth.

• A burst of gamma radiation detected on Earth last year came from a huge explosion in an ancient galaxy, only ~880 million years after the birth of the universe.

The View from Space