Gene Cernan, the last man to walk on the moon,
died on Monday,
January 16. He was 82. NASA didn’t state the cause of Cernan’s death,
but they did note that he had been ill for some time, and was surrounded
by family at the end. In tribute, NASA wrote of Cernan, “A captain in
the U.S. Navy, [he] left his mark on the history of exploration by
flying three times in space, twice to the moon.” Let’s not let the story
of human lunar exploration end with Capt. Cernan. I take leave to
speculate that he wouldn’t want to be the last man
ever to walk on the moon.
Elsewhere in the solar system, the latest data
from Pluto shows us evidence of jagged, spiky, needle-like surface
features called “
penitentes.”
If their presence is confirmed, this would be the first time these icy
formations have been found anywhere other than Earth. On our home
planet, we know these icy spikes can grow up to several feet tall. They
form in higher-altitude environments, where the atmosphere is thinner
and melting ice can sublimate directly away into water vapor, without
ever becoming liquid. Sometimes you can also see them in melting
snowbanks, with all their little points aimed at the sun.
Lead author John Moores says these penitentes
may well be found in other locations across the solar system. Europa is
a prime suspect, because we have radar signatures from the Galileo
spacecraft suggesting similar fields of ice pungees. But Moores says
penitentes may even lurk in places more familiar and closest to home —
like Mars.
Venus, in its turn, has shown us some notable
surface features too, but instead of fields of ice spikes, now there’s a
contender for the largest wave in the solar system hanging out on the
Venusian surface. The researchers
explain
in their study: “The present study shows direct evidence of the
existence of stationary gravity waves, and it further shows that such
stationary gravity waves can have a very large scale – perhaps the
greatest ever observed in the Solar System.”
The standing wave stretches almost from pole to pole. Credit: JAXA/Planet-C/Fukuhara et al., 2017
Observed by the prodigal Japanese spacecraft
Akatsuki, the giant wave is thought to be broadly similar to the way
surface ripples form as water flows over rocks on a stream bed. In this
case, the wave may form as the lower atmosphere flows over mountains on
Venus’ surface. The mammoth waveform is called a gravity wave. Not
gravitational waves; gravity waves. In short, gravity is pulling fluid
whose surface has been disturbed, back to a position of lower
gravitational potential.
Why don’t we see waves like this elsewhere?
Why do we think this one is the biggest? Dr. Alvin Wilson, of the ESA’s
Venus Express mission,
explained
to the BBC that because Venus rotates more slowly than Jupiter, its
surface can support a standing fluid-dynamic feature like this, where
Jupiter’s atmosphere is “broken up into belts” and would have destroyed
the wavefront with turbulence on a planet-wide scale.
Last but not least, scientists are puzzling over something
bright, shiny and new
in the elliptical galaxy Cygnus A. We actually found it some years ago,
but everyone thought it was just an artifact, perhaps of the enormous
black hole at the center of the galaxy. Part of the problem was with the
imaging tech; the bright spot is such a deep red that it barely shows
up in the visible spectrum, so instead of relying only on Hubble’s
snapshots of the region, astronomers compared data from Hubble and Keck
with new observations from the NRAO’s Very Large Array. Sure enough,
it’s not an artifact. But we don’t really know what it is. It’s twice as
bright as any supernova we know of, which makes it puzzling.
Even more puzzling is that the object shows up
in certain shots from Hubble, but not others. Usually, flares this
bright only come from black holes eating something really big. Like
another (much smaller) galaxy. So astronomers are pooling and
circulating their data, trying to get everyone’s eyes on the readings
from that region of the sky so that we can start making hypotheses. As
with so many “we found a thing in space!” stories, the final word: more
telescope time will tell for sure.
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