HUGE BLUE CLOUD CIRCLES THE NORTH POLE
Spaceweather.com
A huge blue cloud of frosted meteor smoke is pinwheeling around the Arctic
Circle. NASA's AIM spacecraft observed its formation on May 20, and it
has since circled the North Pole one and a half times, expanding in size
more than 200-fold. Noctilucent clouds (NLCs) in May are nothing unusual.
They form every year around this time when the first wisps of summertime
water vapour rise to the top of Earth's atmosphere. Molecules of H2O adhere
to specks of meteor smoke, forming ice crystals 80 km above Earth's surface.
When sunbeams hit those crystals, they glow electric-blue. But these NLCs
are different. They are unusually strong and congregated in a coherent
spinning mass, instead of spreading as usual all across the polar cap. This
is most likely a sign of planetary wave activity. Planetary waves are
enormous ripples of temperature and pressure that form in the Earth's
atmosphere in response to Coriolis forces. They are responsible in part for
undulations in the jet stream and can have a major influence on global
weather. All rotating planets with atmospheres have such waves. Data from
NASA's Microwave Limb Sounder (MLS) instruments show that, indeed, a
planetary wave is circling the North Pole in sync with the blue cloud. The
region of coldest temperatures migrates clockwise around the hemisphere,
making one complete lap in about 5 days. This is where the NLCs are
forming.
Because of planetary wave activity, the 2019 season is shaping up to be
unusually good. The clouds have already made an appearance in the USA --
something that usually doesn't happen until late June or July. NLCs have
also been sighted in Europe -- highlighted by a bright display in Germany.
If the 2019 NLC season continues to develop so quickly, even mid-latitude
observers may soon be seeing this polar phenomenon. Observing tip: look
west 30 to 60 minutes after sunset; if you see luminous blue-white tendrils
spreading across the sky, you may have observed a noctilucent cloud.
MARS ROVER FINDS CLAY CACHE
NASA
The Curiosity rover has confirmed that the region on Mars it's exploring,
called the "clay-bearing unit" is well deserving its name. Two samples
the rover recently drilled at rock targets called 'Aberlady' and 'Kilmarie'
have revealed the highest amounts of clay minerals ever found during the
mission. Both drill targets appear in a new selfie taken by the rover on
2019 May 12, the 2,405th Martian day, or sol, of the mission. The clay-
enriched region, located on the side of lower Mount Sharp, stood out to NASA
orbiters before Curiosity landed in 2012. Clay often forms in water, which
is essential for life; Curiosity is exploring Mount Sharp to see if it had
the conditions to support life billions of years ago. The rover's
mineralogy instrument, called CheMin (Chemistry and Mineralogy), provided
the first analyses of rock samples drilled in the clay-bearing unit. CheMin
also found very little haematite, an iron-oxide mineral that was abundant
just to the north, on Vera Rubin Ridge. Other than proof that there was a
significant amount of water once in Gale Crater, what these new findings
mean for the region is still up for debate. It is likely that the rocks in
the area formed as layers of mud in ancient lakes -- something Curiosity
also found lower on Mount Sharp. Water interacted with sediment over time,
leaving an abundance of clay in the rocks there.
ULTRA-SMALL MICROBES SURVIVE IN MARS-LIKE ENVIRONMENT
RAS
The first study of ultra-small bacteria living in the extreme environment
of Ethiopia's Dallol hot springs shows that life can thrive in conditions
similar to those thought to have been found on the young planet Mars.
An international team of researchers has found a strain of the Nanohalo-
archaeles Order bacteria embedded in samples taken from a salt chimney
deposited by supersaturated water at temperatures of 89 degrees Celsius and
at the extremely acidic pH of 0.25. The samples were collected during a
field trip to the Dallol volcano and the Danakil Depression in northern
Ethiopia in January 2017. Precipitation by superheated water saturated with
various salts, including silver chloride, zinc iron sulphide, manganese
dioxide and normal rock-salt, creates Dallol's technicoloured landscape of
yellows, reds, greens and blues. The team collected samples of the thin
layers of salt deposits from the wall of a yellow chimney stack and a blue
pool of water surrounding the outcrop. The samples were transported in
sterile, sealed vials to state-of-the-art facilities in Spain, where they
were analysed using a range of techniques, including electron microscopy,
chemical analysis and DNA sequencing. The team identified tiny, spherical
structures within the salt samples that had a high carbon content, demon-
strating an unambiguously biological origin.
The microorganisms are 50-500 nanometres in diameter -- up to 20 times
smaller than average bacteria. In several cases, the microorganisms are
surrounded by needle-shaped crystals, which suggests that the nanobacteria
may play an active role in the salt deposits and the geochemical cycle at
Dallol. The Dallol volcano and geothermal area is one of the hottest places
on Earth, with average annual temperatures of 36 to 38 degrees Celsius. It
is located at the northern end of the Danakil Depression, which lies around
125m below sea level at the junction of three of the Earth's lithospheric
plates (Arabian, Nubian and Somalian) that are moving apart. Hydrothermal
activity is fuelled by water that has been heated and enriched in gases by a
shallow magma reservoir beneath the volcano. Dallol is surrounded by the
wide Assale salt plain. The interaction between evaporated deposits and
vulcanism creates a unique and complex physical and chemical environment.
The unusual geochemistry of Dallol has close parallels to hydrothermal
environments found on Mars, including the Gusev Crater, where NASA's Spirit
Mars Exploration Rover landed.
MASSIVE MARTIAN ICE DISCOVERY
University of Texas at Austin
Newly discovered layers of ice buried a mile beneath Mars' north pole are
the remnants of ancient polar ice sheets and could be one of the largest
water reservoirs on the planet. The team made the discovery using measure-
ments gathered by the Shallow Radar (SHARAD) on NASA's Mars Reconnaissance
Orbiter (MRO). SHARAD emits radar waves that can penetrate up to a mile and
a half beneath the surface of Mars. The findings are important because the
layers of ice are a record of past climate on Mars in much the same way that
tree rings are a record of past climate on Earth. Studying the geometry and
composition of these layers could tell scientists whether climate conditions
were previously favourable for life. The team found layers of sand and ice
that were as much as 90% water in some places. If melted, the newly
discovered polar ice would be equivalent to a global layer of water around
Mars at least 1.5 metres deep. The authors think that the layers formed
when ice accumulated at the poles during past ice ages on Mars. Each time
the planet warmed, a remnant of the ice caps became covered by sand, which
protected the ice from solar radiation and prevented it from dissipating
into the atmosphere. Scientists have long known about glacial events on
Mars, which are driven by variations in the planet's orbit and tilt. Over
periods of about 50,000 years, Mars leans toward the Sun before gradually
returning to an upright position, like a wobbling spinning top. When the
planet spins upright, the equator faces the Sun, allowing the polar ice
caps to grow. As the planet tilts, the ice caps retreat, perhaps vanishing
entirely. Until now, scientists thought that the ancient ice caps were
lost. The paper shows that in fact significant ice sheet remnants have
survived under the planet's surface, trapped in alternating bands of ice
and sand, like layers in a cake.
NEPTUNE'S MOON FOSTERS RARE ICY UNION
Gemini Observatory
Astronomers using the Gemini Observatory have explored Neptune's largest
moon Triton and observe, for the first time beyond the lab, an extraordinary
union between carbon monoxide and nitrogen ices. The discovery offers
insights into how this volatile mixture can transport material across the
moon's surface via geysers, trigger seasonal atmospheric changes, and
provide a context for conditions on other distant, icy worlds. Extreme
conditions can produce extreme results. In this case, it's the uncommon
pairing of two common molecules -- carbon monoxide (CO) and nitrogen (N2) --
frozen as solid ices on Neptune's frigid moon Triton. In the laboratory, an
international team of scientists has pinpointed a very specific wavelength
of infrared light absorbed when carbon monoxide and nitrogen molecules join
together and vibrate in unison. Individually, carbon monoxide and nitrogen
ices each absorb their own distinct wavelengths of infrared light, but the
tandem vibration of an ice mixture absorbs at an additional, distinct
wavelength identified in this study. Using the 8-metre Gemini South
Telescope in Chile, the team has recorded this same unique infrared
signature on Triton. Key to the discovery was the high-resolution
spectrograph called IGRINS (Immersion Grating Infrared Spectrometer). In
the Earth's atmosphere carbon monoxide and nitrogen molecules exist as
gases, not ices. In fact, molecular nitrogen is the dominant gas in the air
we breathe, and carbon monoxide is a rare contaminant that can be lethal.
On distant Triton, however, carbon monoxide and nitrogen freeze to solid
ices. They can form their own independent ices, or can condense together in
the icy mix detected in the Gemini data. That icy mix could be involved in
Triton's iconic geysers first seen in Voyager 2 spacecraft images as dark,
windblown streaks on the surface of the distant, icy moon. The Voyager 2
spacecraft first captured Triton's geysers in action in the moon's south-
polar region in 1989. Since then, theories have focused on an internal
ocean as one possible source of erupted material. Or the geysers may erupt
when the summertime Sun heats this thin layer of volatile ice on Triton's
surface, potentially involving the mixed carbon monoxide and nitrogen ice
revealed by the Gemini observation. That ice mixture could also migrate
around the surface of Triton in response to seasonally varying patterns of
sunlight. Seasons progress slowly on Triton, as Neptune takes 165 Earth
years to orbit the Sun. A season on Triton lasts a little over 40 years;
Triton passed its southern summer solstice mark in 2000, leaving about 20
more years to conduct further research before its autumn begins. Looking
ahead, the researchers expect that these findings will shed light on the
composition of ices and seasonal variations in the atmosphere on other
distant worlds beyond Neptune. Astronomers have suspected that the mixing
of carbon monoxide and nitrogen ice exists not only on Triton, but also on
Pluto, where the New Horizons spacecraft found the two ices coexisting.
This Gemini finding is the first direct spectroscopic evidence of these
ices mixing and absorbing this type of light on either world.
STELLAR WALTZ WITH DRAMATIC ENDING
University of Bonn
Astronomers have identified an unusual celestial object. It is most likely
the product of the fusion of two stars that died a long time ago. After
billions of years circling around one another these so-called white dwarfs
merged and rose from the dead. In the near future, their lives could
finally end -- with a huge bang. The extremely rare merger product was
discovered by scientists studying images made by the Wide-field Infrared
Survey Explorer (WISE) satellite: they found a gas nebula with a bright star
in its centre. Surprisingly, however, the nebula emitted almost exclusively
infrared radiation and no visible light. The spectrum of the radiation
emitted by the nebula and its central star was analyzed. In that way,
researchers were able to show that the enigmatic celestial object contained
neither hydrogen nor helium -- a characteristic typical for the interiors of
white dwarfs. Stars like our Sun generate their energy through hydrogen
burning, the nuclear fusion of hydrogen. When the hydrogen is consumed,
they continue burning helium. However, they cannot fuse even heavier
elements -- their mass is insufficient to produce the necessary high
temperatures. Once all helium is used up, they cease burning and cool down
turning into white dwarfs. Usually their life is over at this point. But
not for J005311 -- this is how the scientists named their new find in the
constellation Cassiopeia, 10,000 light-years from Earth. Scientists assume
that two white dwarfs formed there in close proximity many billions of years
ago. They circled around each other, creating exotic distortions of space-
time, called gravitational waves. In the process, they gradually lost
energy. In return, the distance between them shrank more and more until
they finally merged. Now their total mass was sufficient to fuse heavier
elements than hydrogen or helium. The stellar furnace started burning
again. Such an event is extremely rare. There are probably not even half
a dozen such objects in the Milky Way.
Nevertheless, the researchers are convinced that they are right with their
interpretation. For one thing, the star in the centre of the nebula shines
40,000 times as brightly as the Sun, far brighter than a single white dwarf
could. In addition, the spectra indicate that J005311 has an extremely
strong stellar wind -- this is the stream of material that emanates from the
stellar surface. Its engine is the radiation generated during the burning
process. But at a speed of 16,000 km/s, the wind of J005311 is so fast that
that factor alone is not enough to explain it. However, merged white dwarfs
are expected to have a very strong rotating magnetic field. Simulations show
that the field acts like a turbine, which additionally accelerates the
stellar wind. Sadly, the resurgence of J005311 will not last long. In only
a few thousand years the star will have transformed all elements into iron
and fade again. As its mass has increased to more than 1.4 times the mass of
the Sun in the merger process, it will suffer an exceptional fate. The star
will collapse under the influence of its own gravity. At the same time, the
electrons and protons building up its matter will fuse into neutrons. The
resulting neutron star has only a fraction of its previous size, measuring
only few kilometres in diameter, while its mass is more than the entire
solar system. J005311, however, won't leave without a final salute. Its
collapse will be accompanied by a supernova explosion.
SUBARU TELESCOPE FINDS 1800 SUPERNOVAE
Kavli Institute for the Physics and Mathematics of the Universe
By combining one of the world's most powerful digital cameras and a
telescope capable of capturing a wider shot of the night sky compared to
other big telescopes, researchers have been able to identify about 1800 new
supernovae, including 58 Type Ia supernovae 8 billion light years away. A
supernova is an exploding star that has reached the end of its life. The
star often becomes as bright as its host galaxy, shining a [US] billion
times brighter than the Sun for any time between a month to six months
before dimming down. Supernovae classed as Type Ia are useful because their
uniform maximum brightness allows researchers to calculate how far the star
is from the Earth. That is particularly useful for researchers who want to
measure the expansion of the Universe. In recent years, researchers began
reporting a new type of supernova five to ten times brighter than Type Ia,
called Super Luminous Supernovae. Many astronomers have been trying to
learn more about these stars. Their unusual brightness enables researchers
to locate them in the farthest parts of the Universe. Since distant
Universe means the early Universe, studying this kind of star could reveal
characteristics about the first, massive stars created after the Big Bang.
But supernovae are rare events, and there are only a handful of telescopes
in the world capable of capturing sharp images of distant stars. In order
to maximize the chances of observing a supernova, astronomers used the
Subaru Telescope, which is capable of generating sharp stellar images; and
the Hyper Suprime-Cam, an 870-mega-pixel digital camera attached to it,
captures a very wide area of the night sky in one shot. By taking repeated
images of the same area of night sky over a six-month period, the
researchers could identify new supernovae by looking for stars that suddenly
appeared brighter before gradually fading out. As a result, the team
identified 5 super-luminous supernovae, and about 400 Type Ia supernovae.
Fifty-eight of the Type Ia supernovae were located more than 8 US-billion
light-years away. In comparison, it took researchers using the Hubble Space
Telescope about 10 years to discover a total of 50 supernovae located more
than 8 billion light-years away. The next step will be to use the data to
calculate a more accurate expansion of the Universe, and to study how dark
energy has changed over time.
NAMES INVITED TO FLY TO MARS
NASA
Members of the public who want to send their names to Mars on NASA's next
rover mission to it (Mars 2020) can get a souvenir boarding pass and their
names etched on microchips to be affixed to the rover. The rover is
scheduled to launch as early as July 2020, with the spacecraft expected to
touch down on Mars in February 2021. The rover, weighing more than 1,000
kilograms, will search for signs of past microbial life, characterize the
planet's climate and geology, collect samples for future return to Earth,
and pave the way for human exploration of Mars. The opportunity to send
your name to Mars comes with a souvenir boarding pass and 'frequent flyer'
points. This is part of a public engagement campaign to highlight missions
involved with NASA's journey from the Moon to Mars. More than 2 million
names flew on NASA's InSight mission to Mars, giving each 'flyer' about 300
million frequent-flyer miles. From now until Sept. 30, you can add your
name to the list and obtain a souvenir boarding pass to Mars here:
https://go.nasa.gov/Mars2020PassNASA will use Mars 2020 and other missions to prepare for human exploration
of the Red Planet. As another step toward that goal, NASA is returning
American astronauts to the Moon in 2024. Government, industry and inter-
national partners will join NASA in a global effort to build and test the
systems needed for human missions to Mars and beyond.
Topic: Mid June Astronomy Bulletin (Read 1110 times)