Astronomy
Collision with Mercury-like object billions of years ago might have created Earth’s magnetic field
Even though we’ve ventured far into the Solar System and our telescopes tell us a lot about distant stars and galaxies, the inner workings of our own planet have remained shrouded in mystery. Much of our understanding of what it’s like underground comes from what are basically educated guesses, because we can’t really send probes down to the center of the Earth. There are some inconsistencies with these models, like why are there certain elements in certain proportions in the planet’s crust and below. Another great problem is the fact that we don’t understand how the Earth’s magnetic field, one of our planet’s most remarkable features, works. Recently, however, scientists from Oxford University have proposed a possible explanation – and it involves a massive collision between our planet in its youth and a smaller cosmic object with similar properties to those of Mercury.
Like all the objects in our Solar System, the Earth formed from a huge molecular cloud which spanned this area of space about 4.6 billion years ago. The early Solar System comprised a young Sun and probably hundreds of planets, which either merged with one another or were destroyed by the gas giants like Jupiter. A lot of what we know about the composition of these celestial objects comes from the study of meteors called chondrites, which have underwent little change since the formation of the Solar System billions of years ago. It is believed these kinds of rocks clumped together under the effect of gravity to create the rocky planets, such as our own.
There is, however, recent data which isn’t entirely consistent with this model, namely there’s a shortage of neodymium relative to samarium (two elements with magnetic properties) in the Earth’s crust and mantle compared to what is found in chondrites. This seems like a rather small and innocuous anomaly, nevertheless it’s something which puzzles scientists, who haven’t managed to come up with a definitive explanation for it. The key, according to Oxford University geochemists Bernard J. Wood and Anke Wohlers, who have recently published a study in the journal Nature, might be sulfur, which made its way into our planet’s crust after it “consumed” a Mercury-like planet the size of Mars early in its lifetime.
The closest planet to the Sun, Mercury is a hellish world which is, quite appropriately, rich in sulfur. If an object with a similar composition had smashed into the Earth billions of years ago, the resulting iron sulfide would have mixed with the neodymium, and subsequently sink together to the core of the planet, leaving relatively more samarium (which is more attracted to the silicate rock found in the crust and mantle and thus less likely to sink) behind in the upper layers. To test this hypothesis, scientists added sulfur to a mixture of elements similar in composition to the primitive Earth, then subjected the sample to the conditions thought to have occurred at that time: temperatures between 1,400 and 1,640 °C (2,550 and 3,000 °F) and pressures of 1.5 gigapascals (150,000 times greater than atmospheric pressure at sea level today!). After adding sufficient quantities of sulfur, neodymium sunk to the core of the model planet, which is consistent with the theory.
This could also help explain the origin of the Earth’s magnetic field. The planet’s inner core is mainly made up of iron which is extremely hot (about 5,700 °C or 10,300 °F), however due to the huge pressure at that depth it remains solid. Higher up, where the pressure isn’t as high, there’s an outer core of molten iron. Convection currents, as well as the Coriolis force cause the flow of torrents of liquid iron, generating electric currents, which then produce magnetic fields. How the core has remained molten for so long is another mystery, which could be explained by uranium (which generates heat through nuclear decay) also sinking together with the iron sulfide.
If a catastrophic collision with a Mercury-like, Mars-sized object sounds a bit far-fetched, it shouldn’t. Remember there were perhaps hundreds of objects of various sizes and compositions in the young Solar System, which were constantly jostling for position. It’s not inconceivable that many of them collided, getting obliterated and forming new celestial bodies or merging together. In fact, one of the most widely accepted theories regarding the Moon’s formation holds that the Earth collided with a planet similar in size to Mars we now call Theia, and the debris resulting from the crash clumped together to form our sole natural satellite.
Artist’s depiction of the impact between the Earth and a planet-sized object called Theia, which could have resulted in the formation of the Moon. Scientists believe a similar impact could have created our planet’s magnetic field. Image: NASA/JPL-Caltech.
Our magnetic field is extremely important for life on Earth. It protects us from potentially devastating solar winds and cosmic rays, which would otherwise blow away the upper parts of the atmosphere, and it also helps birds, turtles, and even humans navigate. You could argue we wouldn’t be here if it didn’t exist. Although the collision with a Mercury-like object hypothesis is still far from being confirmed, it’s still interesting to think life on Earth was made possible by a cataclysmic event early in our planet’s lifetime.
Astronomy
Witness the rare celestial event of Mars and Jupiter reaching their closest proximity in the sky this week, a phenomenon that will not occur again until 2033.
Mars and Jupiter will be only 0.3 degrees apart in the sky on August 14. From our point of view, this passage is very close. If you miss it, you won’t be able to see another one until 2033.
When two objects pass each other in the sky from our point of view, this is called a conjunction. Every time two planets came together, the closer one would block out the other because they would all be moving in a perfectly flat plane. The orbits of the planets are slightly different from those of the other planets, though, so they move slightly to the north and south of each other. Every time, that gap is a different size.
When two things happen close together, the results are especially stunning. Jupiter and Saturn were close enough to each other in 2020 that they could be seen in the same field of view through a telescope. This is a treat for people who like to observe the sky.
Being 0.5 degrees wide, the full moon will fit in any view that can hold the whole moon. This pair will also look good before and after the full moon.
But even with the naked eye, a close conjunction can make the sky look even more amazing. The contrast between the red of Mars and the white of Jupiter will be especially striking. However, Mars’ brightness changes a lot. When it’s at its brightest, it’s about the same brightness as Jupiter. Right now, it’s 16 times less bright. They are so bright that, unless there are clouds, you should be able to see them from all but the dirtiest cities.
Most people in the world will miss this sight, though, because they can’t see the pair of planets in the evening from anywhere on Earth. The exact time they rise depends on where you live, but it’s usually between midnight and 3 am. To see this, you will mostly need to get up before astronomical twilight starts so that you have time to get through the thickest part of the atmosphere.
For people in Europe, Africa, west Asia, and the Americas, the closest time will be 14:53 UTC, which is during the day. The mornings before and after, though, will look almost as close.
Mars and Jupiter meet about every two and a half years, but the most recent one was almost twice as far away and could only be seen in the morning. In 2029, the gaps will be just under two degrees. The next one will be even wider, at more than a degree.
When planets are close to each other, that doesn’t always mean that their distance from each other is very small. Mars has been around the Sun for 687 days, but it is now less than 100 days past its perihelion, which means it is closer than usual. Even though Jupiter is a little closer than usual, it’s not really that close. To be as close as possible to each other, Mars has to be at its farthest point, and Jupiter has to be at its closest point. So this one is not unusual.
But if you want to see something beautiful, you will have to wait more than nine years to see it again.
To figure out if there is life in other parts of the universe, we start with Earth, where there is life now. Finding another Earth is a good way to find aliens. We have found more than 5,000 exoplanets, but we haven’t found Earth’s twin yet. This could change soon, though. Here comes the PLATO mission from the European Space Agency (ESA).
What does PLATO stand for? It stands for PLAnetary Transits and Oscillations of stars. Its goal is very clear. It will look for nearby stars like the Sun that might have habitable worlds like Earth.
“One of the main goals is to find a way to compare Earth and the Sun.” The size of Earth is in the habitable zone of a star like the Sun. “We want to find it around a star that’s bright enough that we can really figure out how heavy it is and how big it is,” Dr. David Brown from the University of Warwick told IFLScience. “If you like, that’s our main goal.”
The telescope is not only an observatory for looking for planets, but it is also an observatory for collecting data on a huge number of stars. The mission team thinks that the fact that it can do both is a key part of why this telescope will be so important.
“You have two parts of the mission.” One is exoplanets, and the other is the stars. “From a scientific point of view, I think it’s pretty cool that these two parts are working together to make the best science we can,” Dr. Brown said.
One of the secondary goals is to make a list of all the planets that are Earth-like and all the star systems that are out there. One more goal is to find other solar systems that are like ours. Even though we don’t know for sure if our little part of the universe is truly unique, it does seem to be different from everything else.
Dr. Brown told IFLScience, “We have a bunch of other scientific goals.” “Really, how well do we know how planetary systems change and grow over time?” Planetary systems are something we’re trying to understand as a whole, not just one planet at a time.
PLATO is different in more ways than just the goals. It is not just one telescope. In fact, it’s made up of 26 different ones. Two of the cameras are fast, and the other 24 are normal cameras set up in groups of six with a small gap between them. This makes the telescope work better, has a wider field of view, and lets you quickly rule out false positives.
It can be hard to tell which of the things you find when you transit exoplanets are real and which ones are not. With the help of several telescopes, we were able to block out some of the mimics that we would have seen otherwise. “Plus, it looks pretty cool,” Dr. Brown said with excitement. “This big square with all of these telescopes pointing at you looks really cool!”
This week, Dr. Brown gave an update on PLATO at the National Astronomy Meeting at the University of Hull. The telescope is being put together and has recently passed important tests. There are no changes to the planned launch date for December 2026. An Ariane 6 rocket, the same kind that made its first launch last week, will take off from French Guiana.
Gravitational waves can be turned into sound very easily. The little chirp changes into little sounds as soon as the blocks hit each other. One of those chirps is my ringtone when my phone has sound, which doesn’t happen very often. The people at Audio Universe have now made the gravitational wave data even better.
In a 3D video, the sounds of gravitational waves hit you from the direction in the sky where it is thought they came from. The sound effects and visualization are both great. There are tiny vibrations in space-time that can hit you as you move your mouse, phone, or VR headset.
Like other sonification projects, it gives blind and visually impaired people a way to get involved in astronomy. It works well with other methods like the Tactile Universe. But that’s not the only reason why they do it.
“We want to do this for three reasons.” It helps researchers look into big, complicated datasets with lots of dimensions. It could be used to make educational materials that are immersive and interesting. Rose Shepherd from Newcastle University says, “It can also make astronomy easier for more people to understand, which is an important thing.” “Making things easier to get makes them better for everyone.”
Being able to listen to the emission lines of celestial objects is one of the most interesting things about sonification for research. As an object moves, its light spectrum peaks spread out, and sonification can make something that is barely noticeable to the eye seem very clear to the ear.
This is helpful in more than one field, though. The group has thought about how adding sound to different datasets could make them better. Warming Stripes is a cool example of this. This is a simple image that shows changes in temperature over time by using a series of stripes, from blue to red. The stripes on the right side get redder as we move from the left to the right. The left side shows decades ago. It is great to see how the climate crisis is getting worse, and now sound adds a little more to it.
“By adding sounds, it can give your data an emotional meaning.” Shepherd explained, “You can use that to show the data how you feel.” “We didn’t mean for the Warming Stripes sonification to make people feel stressed, but it was interesting to see how they reacted instead of just watching the video.”
Audio Universe is making a sonic toolkit that many people can use to make their own resources.
She gave a talk about the audio universe at the National Astronomy Meeting at the University of Hull this week.
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