Sven Bronson, a Swedish astronomer working at an observatory in South Africa, discovers a pair of rogue planets, Bronson Alpha and Bronson Beta, which will soon enter the Solar System. In eight months, they will pass close enough for gravitational forces to cause catastrophic damage to the Earth. Sixteen months later, after swinging around the Sun, Bronson Alpha (a gas giant) will return to pulverize the Earth and depart. Bronson Beta (discovered to be Earth-like and potentially habitable) may remain and assume a stable orbit.
Scientists led by Cole Hendron work desperately to build an atomic rocket to transport enough people, animals and equipment to Bronson Beta to save humanity from extinction. Various countries do the same. The United States evacuates coastal regions in preparation for the first encounter. As the planets approach, observers see through their telescopes cities on Bronson Beta. Tidal waves sweep inland at a height of 750 feet (230 m), volcanic eruptions and earthquakes add to the deadly toll, and the weather runs wild for more than two days. Bronson Alpha grazes and destroys the Moon.
Three men take a floatplane to check out conditions across the United States and meet with the President in Hutchinson, Kansas, the temporary capital of the United States. All three are wounded fighting off a mob at their last stop, but manage to return with a precious sample of an extremely heat-resistant metal one of them had noticed. This solves the last remaining engineering obstacle: no material had been found before to make rocket tubes capable of withstanding the heat of the atomic exhaust.
But truth is, the Earth did once collide with another world. The debris from that ancient collision formed the Moon. But what happened with the colliding planet?
A new paper discusses the fate of Theia, the colliding planet. I had heard about these blobs in the Earth back in the Eighties, when they were believed (and many still believe) to be sunken oceanic plates. But maybe they are something more!:
Scientists widely agree that an ancient planet likely smashed into Earth as it was forming billions of years ago, spewing debris that coalesced into the moon that decorates our night sky today.
The theory, called the giant-impact hypothesis, explains many fundamental features of the moon and Earth.
But one glaring mystery at the center of this hypothesis has endured: What ever happened to Theia? Direct evidence of its existence has remained elusive. No leftover fragments from the planet have been found in the solar system. And many scientists assumed any debris Theia left behind on Earth was blended in the fiery cauldron of our planet’s interior.
A new theory, however, suggests that remnants of the ancient planet remain partially intact, buried beneath our feet.
Molten slabs of Theia could have embedded themselves within Earth’s mantle after impact before solidifying, leaving portions of the ancient planet’s material resting above Earth’s core some 1,800 miles (about 2,900 kilometers) below the surface, according to a study published Wednesday in the journal Nature.
...They were already aware that there are two massive, distinct blobs that are embedded deep within the Earth. The masses — called large low-velocity provinces, or LLVPs — were first detected in the 1980s. One lies beneath Africa and another below the Pacific Ocean.
These blobs are thousands of kilometers wide and likely more dense with iron compared with the surrounding mantle, making them stand out when measured by seismic waves. But the origins of the blobs — each of which are larger than the moon — remain a mystery to scientists.
But for Dr. Qian Yuan, a geophysicist and postdoctoral fellow at the California Institute of Technology and the new study’s lead author, his understanding of LLVPs forever changed when he attended a 2019 seminar at Arizona State University, his alma mater, that outlined the giant-impact hypothesis.
That’s when he learned new details about Theia, the mysterious projectile that presumably struck Earth billions of years ago.
And, as a trained geophysicist, he knew of those mysterious blobs hidden in Earth’s mantle.
Yuan had a eureka moment, he said.
Immediately, he began perusing scientific studies, searching to see whether someone else had proposed that LLVPs might be fragments of Theia. But no one had.
...Their work, which assigned a certain size to Theia and speed of impact in the modeling, suggested that the ancient planet’s collision likely did not entirely melt Earth’s mantle, allowing the remnants of Theia to cool and form solid structures instead of blending together in Earth’s inner stew.
...The combination of high-resolution giant impact and mantle convection simulations, mineral physics calculations, and seismic imaging suggests that the lower half of Earth’s mantle remained mostly solid after this impact, and that parts of Theia’s iron-rich mantle sank and accumulated atop Earth's core nearly 4.5 billion years ago, surviving there throughout Earth’s history.
...Dr. Seth Jacobson, an assistant professor of planetary science at Michigan State University, acknowledged that the theory may not, however, soon reach broad acceptance.
...One other theory, for example, posits that LLVPs are actually heaps of oceanic crust that have sunk to the depths of the mantle over billions of years.
“I doubt the advocates for other hypotheses (about LLVP formation) are going to abandon them just because this one has appeared,” Jacobson added. “I think we’ll be debating this for quite some time.”
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