After a six-year journey, a plucky spacecraft called Hayabusa2 zinged
back into Earth’s atmosphere in late 2020 and landed deep in the
Australian outback. When researchers from the Japanese space agency JAXA
opened it, they found its precious payload sealed and intact: a handful
of dirt that Hayabusa2 managed to scoop off the surface of a speeding
asteroid.
Scientists
have now begun to announce the first results from the analysis of this
extraordinary sample. What they found suggests that this asteroid is a
piece of the same stuff that coalesced into our sun four-and-a-half
billion years ago.
“We previously only had a handful of
these rocks to study, and all of them were meteorites that fell to Earth
and were stored in museums for decades to centuries, which changed
their compositions,” said geochemist Nicolas Dauphas, one of the three
University of Chicago researchers who worked with a Japan-led
international team of scientists to analyze the fragments. “Having
pristine samples from outer space is simply incredible. They are
witnesses from parts of the solar system that we have not otherwise
explored.“ …
How we think about our planet’s center may need to be seriously updated.
New
evidence suggests that, instead of consistently rotating faster than
Earth’s spin, the solid inner core oscillates – spinning first in one
direction with respect to the surface far above, then the other,
changing direction every six years.
This not only has implications for our understanding of the inner
workings of our home world, it can also neatly explain a mystery that
has perplexed scientists for some time: an oscillating variation in the length of Earth’s day, with a period of 5.8 years.
“From our findings, we can see the Earth’s surface shifts compared to its inner core, as people have asserted for 20 years,” said geophysicist John E. Vidale of the University of Southern California, Los Angeles (UCLA).
“However,
our latest observations show that the inner core spun slightly slower
from 1969-71 and then moved the other direction from 1971-74. We also
note that the length of a day grew and shrank as would be predicted. The
coincidence of those two observations makes oscillation the likely
interpretation.”
Although our understanding of Earth’s core has
developed a lot in recent decades, there’s still a lot we don’t know. We
can’t just go there and take a gander at it; everything we know, we’ve
gleaned from indirect observations, such as seismic waves propagating
and bouncing through the entire planet.
But
this is still a very effective tool. Scientists have been able to
ascertain that Earth’s inner core is probably a hot, dense ball of solid
iron, measuring roughly 2,440 kilometers (1,516 miles) across, a little
bigger than the size of Pluto. Evidence also suggests that it demonstrates superrotation, rotating faster than Earth itself. …
