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Head-on Collision With Another Planet Formed Earth and Moon

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Our galactic neighborhood is pretty peaceful these days. So peaceful, in fact, that it’s easy to forget its violent and spectacular beginnings. Fortunately, we have scientists to remind us. A paper published last week in the journal Science reports that Earth once smashed into, then mixed with, another planet. They say the Moon formed out of the resulting wreckage too.

That planet’s name was Theia. At the time of the collision, Theia was so young that researchers refer to it as a “planetary embryo.” Though it's important to note that Earth was only 100 million years old itself—also young in cosmic time.

While knowledge of the planets’ collision isn't new, the paper's co-authors uncovered new details of the event. Most scientists believed the impact had occurred at a 45-degree angle, like one car sideswiping another. But this new research shows it was probably more like a brutal head-on collision. 

How can you be sure about something that happened to our planet nearly 4.5 billion years ago? Take a good look at the Moon. Researchers tested lunar rock samples collected by astronauts on the Apollo 12, 15, and 17 missions. They also looked at six volcanic rocks from Hawaii and Arizona. The scientists focused on the rocks’ chemical makeup—specifically on their oxygen atoms.

Researchers Paul Warren, Edward Young and Issaku Kohl with a moon rock sample. Image Credit: Christelle Snow/UCLA

There are several isotopes of oxygen, each named for its number of protons and neutrons. O-16, which makes up nearly all of the oxygen on Earth (including in rocks), has eight protons and eight neutrons. We also have small quantities of O-17 and O-18. The ratio of these three isotopes acts as a chemical signature, so if two entities have the same ratio, it’s likely they’re made of the same stuff.

The theory was that Theia’s hit-and-run impact flung shards of both planets outward into space, where gravitational forces compressed them into a single ball: the Moon. If that’s so, then the Moon’s ratio of isotopes should look different from Earth’s. And some scientists believe that’s the case.

But the researchers behind the new paper argue otherwise. "We don't see any difference between the Earth's and the moon's oxygen isotopes; they're indistinguishable," lead author Edward Young said in a press release

What does this mean? It means, the researchers say, that Theia hit Earth hard and fast, and likely straight-on. Some of the debris from Theia and Earth combined to form the planet we call home today, and some of it combined to form the Moon. 

"Theia was thoroughly mixed into both the Earth and the Moon, and evenly dispersed between them," Young said. "This explains why we don't see a different signature of Theia in the Moon versus the Earth."

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Space
It's Official: Uranus Smells Like Farts
NASA, JPL-Caltech
NASA, JPL-Caltech

Poor Uranus: After years of being the butt of many schoolyard jokes, the planet's odor lives up to the unfortunate name. According to a new study by researchers at the University of Oxford and other institutions, published in the journal Nature Astronomy, the upper layer of Uranus's atmosphere consists largely of hydrogen sulfide—the same compound that gives farts their putrid stench.

Scientists have long suspected that the clouds floating over Uranus contained hydrogen sulfide, but the compound's presence wasn't confirmed until recently. Certain gases absorb infrared light from the Sun. By analyzing the infrared light patterns in the images they captured using the Gemini North telescope in Hawaii, astronomers were able to get a clearer picture of Uranus's atmospheric composition.

On top of making farts smelly, hydrogen sulfide is also responsible for giving sewers and rotten eggs their signature stink. But the gas's presence on Uranus has value beyond making scientists giggle: It could unlock secrets about the formation of the solar system. Unlike Uranus (and most likely its fellow ice giant Neptune), the gas giants Saturn and Jupiter show no evidence of hydrogen sulfide in their upper atmospheres. Instead they contain ammonia, the same toxic compound used in some heavy-duty cleaners.

"During our solar system's formation, the balance between nitrogen and sulfur (and hence ammonia and Uranus’s newly detected hydrogen sulfide) was determined by the temperature and location of planet’s formation," research team member Leigh Fletcher, of the University of Leicester, said in a press statement. In other words, the gases in Uranus's atmosphere may be able to tell us where in the solar system the planet formed before it migrated to its current spot.

From far away, Uranus's hydrogen sulfide content marks an exciting discovery, but up close it's a silent but deadly killer. In large enough concentrations, the compound is lethal to humans. But if someone were to walk on Uranus without a spacesuit, that would be the least of their problems: The -300°F temperatures and hydrogen, helium, and methane gases at ground level would be instantly fatal.

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Feeling Anxious? Just a Few Minutes of Meditation Might Help
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Some say mindfulness meditation can cure anything. It might make you more compassionate. It can fix your procrastination habit. It could ward off germs and improve health. And it may boost your mental health and reduce stress, anxiety, depression, and pain.

New research suggests that for people with anxiety, mindfulness meditation programs could be beneficial after just one session. According to Michigan Technological University physiologist John Durocher, who presented his work during the annual Experimental Biology meeting in San Diego, California on April 23, meditation may be able to reduce the toll anxiety takes on the heart in just one session.

As part of the study, Durocher and his colleagues asked 14 adults with mild to moderate anxiety to participate in an hour-long guided meditation session that encouraged them to focus on their breathing and awareness of their thoughts.

The week before the meditation session, the researchers had measured the participants' cardiovascular health (through data like heart rate and the blood pressure in the aorta). They evaluated those same markers immediately after the session ended, and again an hour later. They also asked the participants how anxious they felt afterward.

Other studies have looked at the benefits of mindfulness after extended periods, but this one suggests that the effects are immediate. The participants showed significant reduction in anxiety after the single session, an effect that lasted up to a week afterward. The session also reduced stress on their arteries. Mindfulness meditation "could help to reduce stress on organs like the brain and kidneys and help prevent conditions such as high blood pressure," Durocher said in a press statement, helping protect the heart against the negative effects of chronic anxiety.

But other researchers have had a more cautious outlook on mindfulness research in general, and especially on studies as small as this one. In a 2017 article in the journal Perspectives on Psychological Science, a group of 15 different experts warned that mindfulness studies aren't always trustworthy. "Misinformation and poor methodology associated with past studies of mindfulness may lead public consumers to be harmed, misled, and disappointed," they wrote.

But one of the reasons that mindfulness can be so easy to hype is that it is such a low-investment, low-risk treatment. Much like dentists still recommend flossing even though there are few studies demonstrating its effectiveness against gum disease, it’s easy to tell people to meditate. It might work, but if it doesn't, it probably won't hurt you. (It should be said that in rare cases, some people do report having very negative experiences with meditation.) Even if studies have yet to show that it can definitively cure whatever ails you, sitting down and clearing your head for a few minutes probably won't hurt.

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