Venus is a strange, extreme sort of
planet for lots of reasons. For one thing
it rotates so slowly that its day is
longer than its year. Combine that with
its chokingly thick atmosphere and you
end up with one of the least windy
surfaces in the solar system. Fly up high
though you'll find the clouds rushing by
a blistering 360 km/h. That's why
astronomers with Japan's Akatsuki
spacecraft were so shocked to find a
giant stationary feature in Venus's
cloud tops. This new finding was the
result of some of the first observations
by Akatsuki and was announced this week
in the journal Nature Geoscience. The
authors describe what they saw as an
enormous bow structure like the shape
created by a boat cutting through the
water.
It spanned 10,000 kilometers of Venus's
sky distorting an entire hemisphere's
worth of clouds at an altitude of 65
kilometers and seemed hotter than the
surrounding atmosphere. If it moved like
a normal cloud this thing should have
been circling Venus pretty quickly.
Instead, four days later it had hardly
budged and when Akatsuki was able to
observe the area again about a month
later it was gone. Now, when the researchers
plotted of the structure's position on a map
of Venus surface they found it sitting
smack-dab in the center of a mountainous
region called Aphrodite Terra. This led
them to conclude that Akatsuki had
spotted a huge example of a feature
that's common here on earth,
what's known as a gravity wave. These kind of waves
happen when buoyancy pushes up a
fluid like air or water and gravity
pulls it back down. Gravity waves are not
the same thing as gravitational waves,
the ripples in space-time caused by
things like merging black holes. The most
common gravity waves on earth are the
ones that surfers ride on but they can
also form in the atmosphere often when
air rushes over the top of a mountain.
The feature is seen on Venus just
downwind of a big peak, so it's probably
created by rushing air over that peak.
Even though it's common for waves like
these to stay in one place, when they
reach such a massive scale, they usually
move at the speed of the surrounding wind.
Now that's clearly not the case here
and the researchers don't know why the
wave stayed still or why it later
disappeared. They also aren't sure of how
a wave like this could end up so high in
Venus's atmosphere, but simulations show
that if it can reach a height of 10 kilometers,
getting the rest of the way would be a lot
easier, and if the surface winds on Venus
turn out to be more dynamic than we
thought in the past they could create
waves that high. Akatsuki is slated to
operate well into 2018, so with more
observations hopefully we'll learn
exactly how this giant wave came to
exist and where it went.
Now this was also a big week for
spaceflight. Just four months after an
explosion on the pad claimed a rocket
and its payload, SpaceX was back in
action with a satellite launch last
Saturday. The launch came less than two
weeks after the conclusion of the
accident investigation. The report, a
joint effort between SpaceX and federal
agencies, determined that the company's
Falcon 9 exploded after the failure
of an internal tank. This small tank,
called the composite overwrapped pressure
vessel, holds the helium needed to
pressurize the rocket's liquid oxygen fuel.
Buckles in the wall of the tank formed
gaps that allowed super-cold oxygen to
pool in the area where friction could
ignite it, causing the explosion. By
returning to an older tank fueling
process SpaceX got permission to
resume their flight schedule. On board
the Falcon 9 were ten satellites for
communications company Iridium, the first
of at least seventy that SpaceX is set to
launch. The rocket's first stage also made
a picture-perfect touchdown on a
floating platform in the Pacific Ocean,
the first such landing off the West
Coast and that's just the start of the
company's plans for this year. They're still
catching up after September's accident,
and they're also planning the inaugural
flight of the much larger Falcon Heavy
rocket, which is capable of launching
more than fifty-four metric tons to
low-earth orbit. They're also hoping to
launch one of their previously landed
rockets for the first time. If all goes
well these used rockets could
dramatically cut the cost of sending
stuff into space. Then there's the
contract with NASA to launch astronauts
to the International Space Station.
Test flights of the human ready Dragon
capsule could begin late this year with
a 2018 goal for the first crewed mission.
I don't know about you, but I am excited,
and a little nervous, to see how that goes.
If you want to learn more about these
kinds of discoveries and missions as
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October of 2015, we told you bit about the five
finalists for Discovery's next-generation of
missions. Those five teams spent the last year or so
beefing of their proposals and finally
NASA has made a decision.