Monthly Archives: September 2015

Liquid water flows on today’s Mars: NASA confirms evidence

New findings from NASA’s Mars Reconnaissance Orbiter (MRO)
provide the strongest evidence yet that liquid water flows intermittently on
present-day Mars.

Using an imaging spectrometer on MRO, researchers detected
signatures of hydrated minerals on slopes where mysterious streaks are seen on
the Red Planet. These darkish streaks appear to ebb and flow over time. They
darken and appear to flow down steep slopes during warm seasons, and then fade
in cooler seasons. They appear in several locations on Mars when temperatures
are above minus 10 degrees Fahrenheit (minus 23 Celsius), and disappear at
colder times.

Martian slopes. Credit: NASA/JPL-Caltech/Univ. of Arizona

“Our quest on Mars has been to ‘follow the water,’ in
our search for life in the universe, and now we have convincing science that
validates what we’ve long suspected,” said John Grunsfeld, astronaut and
associate administrator of NASA’s Science Mission Directorate in Washington.
“This is a significant development, as it appears to confirm that water —
albeit briny — is flowing today on the surface of Mars.”

These downhill flows, known as recurring slope lineae (RSL),
often have been described as possibly related to liquid water. The new findings
of hydrated salts on the slopes point to what that relationship may be to these
dark features. The hydrated salts would lower the freezing point of a liquid
brine, just as salt on roads here on Earth causes ice and snow to melt more
rapidly. Scientists say it’s likely a shallow subsurface flow, with enough
water wicking to the surface to explain the darkening.

“We found the hydrated salts only when the seasonal
features were widest, which suggests that either the dark streaks themselves or
a process that forms them is the source of the hydration. In either case, the
detection of hydrated salts on these slopes means that water plays a vital role
in the formation of these streaks,” said Lujendra Ojha of the Georgia
Institute of Technology (Georgia Tech) in Atlanta, lead author of a report on
these findings published Sept. 28 by Nature Geoscience.

Ojha first noticed these puzzling features as a University
of Arizona undergraduate student in 2010, using images from the MRO’s High
Resolution Imaging Science Experiment (HiRISE). HiRISE observations now have
documented RSL at dozens of sites on Mars. The new study pairs HiRISE
observations with mineral mapping by MRO’s Compact Reconnaissance Imaging
Spectrometer for Mars (CRISM).

The spectrometer observations show signatures of hydrated
salts at multiple RSL locations, but only when the dark features were
relatively wide. When the researchers looked at the same locations and RSL
weren’t as extensive, they detected no hydrated salt.

Ojha and his co-authors interpret the spectral signatures as
caused by hydrated minerals called perchlorates. The hydrated salts most
consistent with the chemical signatures are likely a mixture of magnesium
perchlorate, magnesium chlorate and sodium perchlorate. Some perchlorates have
been shown to keep liquids from freezing even when conditions are as cold as
minus 94 degrees Fahrenheit (minus 70 Celsius). On Earth, naturally produced
perchlorates are concentrated in deserts, and some types of perchlorates can be
used as rocket propellant.

Perchlorates have previously been seen on Mars. NASA’s
Phoenix lander and Curiosity rover both found them in the planet’s soil, and
some scientists believe that the Viking missions in the 1970s measured signatures
of these salts. However, this study of RSL detected perchlorates, now in
hydrated form, in different areas than those explored by the landers. This also
is the first time perchlorates have been identified from orbit.

MRO has been examining Mars since 2006 with its six science
instruments.
“The ability of MRO to observe for multiple Mars years
with a payload able to see the fine detail of these features has enabled
findings such as these: first identifying the puzzling seasonal streaks and now
making a big step towards explaining what they are,” said Rich Zurek, MRO
project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California.

For Ojha, the new findings are more proof that the
mysterious lines he first saw darkening Martian slopes five years ago are,
indeed, present-day water.

“When most people talk about water on Mars, they’re
usually talking about ancient water or frozen water,” he said. “Now
we know there’s more to the story. This is the first spectral detection that
unambiguously supports our liquid water-formation hypotheses for RSL.”

The discovery is the latest of many breakthroughs by NASA’s
Mars missions.

“It took multiple spacecraft over several years to
solve this mystery, and now we know there is liquid water on the surface of
this cold, desert planet,” said Michael Meyer, lead scientist for NASA’s
Mars Exploration Program at the agency’s headquarters in Washington. “It
seems that the more we study Mars, the more we learn how life could be supported
and where there are resources to support life in the future.”

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Meteorite from birth of solar system to go on display

An extremely rare meteorite that has the same make-up as the
primordial solar system goes on public display for the first time on Friday at
the Natural History Museum in London.
The Ivuna meteorite landed in Tanzania in 1938 and has since
been broken up into samples, the rest of which remain in the hands of private
collectors. The Natural History Museum bought the largest lump in 2008 from a
private enthusiast in the US.
The black, satsuma-sized space rock dates back to the birth
of the solar system some 4.6bn years ago, before the Earth had formed. It is
one of only five in the world with a ratio of chemical elements that, save for
hydrogen and helium, almost exactly matches that of the sun.
The meteorite is a carbonaceous chondrite and has a lot of
water locked up in its minerals. Up to a fifth of the rock’s weight is bound
water, with other constituents being organic compounds that are considered the
building blocks of life.
Meteorites like the Ivuna rock may have brought water and
vital compounds for life on Earth when they slammed into the surface of the
fledgling planet billions of years ago.
Ashley King, a postdoctoral researcher at the Natural
History Museum in London, said: “These meteorites are a unique record of
conditions that existed at the time over 4.5 billion years ago, before the
Earth had formed. They are the primordial building blocks of our Solar System.”
When carbonaceous chondrites reach the Earth, they start to
react in the air. But the museum’s Ivuna sample has been stored in a case in
pure nitrogen for most of its life to preserve the pristine material.

Researchers at the Natural History Museum believe that
studying the meteorite might give them a more accurate record of the sun’s
composition than measuring the sun’s surface itself.
“Ivuna is actively used in our research, and it is fantastic
to be able to show visitors a unique specimen that is older than Earth itself,”
said King. The speciment will go on display at the museum’s free after-hours
event, Science Uncovered, on 25 September.
Sara Russell, head of mineral and planetary sciences at the
museum, said the Ivuna meteorite had recently been used to cast doubt on claims
that the orbiting XMM-Newton observatory had seen dark matter streaming from a
distant cluster of galaxies.
“It highlights that we need to learn more about our own
galactic back yard. By studying the solar system we can learn abut how matter
behaves in distant galaxies. At the Natural History Museum, we are using
meteorites such as Ivuna, which dates from a time before planets existed, to
understand the composition of primordial material at that time,” she said.

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On this day in history: the rings around Jupiter were declared to be made of dust

On 15th September 1998, the rings around the
planet Jupiter were declared to be made of dust from the impacts of cosmic
bodies that crashed into Jupiter’s moons. The idea came from studies of the
rings made by scientists at several institutions.

Jupiter is the fifth planet from the Sun and the largest
planet in the Solar System. It is a giant planet with a mass one-thousandth
that of the Sun, but is two and a half times that of all the other planets in
the Solar System combined. Jupiter is a gas giant, along with Saturn (Uranus
and Neptune are ice giants). 

Jupiter was known to astronomers of ancient times.
The Romans named it after their god Jupiter. When viewed from Earth, Jupiter
can reach an apparent magnitude of −2.94, bright enough to cast shadows, and
making it on average the third-brightest object in the night sky after the Moon
and Venus.

A portrait of Jupiter. Source: NASA
Jupiter is primarily composed of hydrogen with a quarter of
its mass being helium, although helium only comprises about a tenth of the
number of molecules. It may also have a rocky core of heavier elements, but
like the other giant planets, Jupiter lacks a well-defined solid surface.
Because of its rapid rotation, the planet’s shape is that of an oblate spheroid
(it has a slight but noticeable bulge around the equator). 

The outer atmosphere
is visibly segregated into several bands at different latitudes, resulting in
turbulence and storms along their interacting boundaries. A prominent result is
the Great Red Spot, a giant storm that is known to have existed since at least
the 17th century when it was first seen by telescope. 

Surrounding Jupiter is a
faint planetary ring system and a powerful magnetosphere. Jupiter has at least
67 moons, including the four large Galilean moons discovered by Galileo Galilei
in 1610. Ganymede, the largest of these, has a diameter greater than that of
the planet Mercury.

Jupiter has been explored on several occasions by robotic
spacecraft, most notably during the early Pioneer and Voyager flyby missions
and later by the Galileo orbiter. The most recent probe to visit Jupiter was
the New Horizons spacecraft in late February 2007 en route to Pluto, using the
gravity from Jupiter to increase its speed and bend its trajectory. Future
targets for exploration in the Jovian system include the possible ice-covered
liquid ocean on the moon Europa.

The Galileo orbiter, which went into orbit around Jupiter on
December 7, 1995 orbited the planet for over seven years, conducting multiple
flybys of all the Galilean moons and Amalthea. The spacecraft also witnessed
the impact of Comet Shoemaker–Levy 9 as it approached Jupiter in 1994, giving a
unique vantage point for the event. While the information gained about the
Jovian system from Galileo was extensive, its originally designed capacity was
limited by the failed deployment of its high-gain radio transmitting antenna.

A 340-kilogram titanium atmospheric probe was released from
the spacecraft in July 1995, entering Jupiter’s atmosphere on December 7. It
parachuted through 150 km (93 mi) of the atmosphere at speed of about 2,575
km/h (1600 mph)[28] and collected data for 57.6 minutes before it was crushed
by the pressure of about 23 atmospheres at a temperature of 153 °C. It would
have melted thereafter, and possibly vaporized. The Galileo orbiter itself
experienced a more rapid version of the same fate when it was deliberately
steered into the planet on September 21, 2003, at a speed of over 50 km/s, to
avoid any possibility of it crashing into and possibly contaminating Europa—a
moon which has been hypothesized to have the possibility of harboring life.

Data from this mission revealed that hydrogen composes up to
90% of Jupiter’s atmosphere. The temperatures data recorded was more than 300
°C (>570 °F) and the windspeed measured more than 644 kmph (>400 mph)
before the probes vapourised.

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What happened to early Mars’ atmosphere? New study eliminates one theory

Scientists may be closer to solving the mystery of how Mars
changed from a world with surface water billions of years ago to the arid Red
Planet of today.

A new analysis of the largest known deposit of carbonate
minerals on Mars suggests that the original Martian atmosphere may have already
lost most of its carbon dioxide by the era of valley network formation.

“The biggest carbonate deposit on Mars has, at most,
twice as much carbon in it as the current Mars atmosphere,” said Bethany
Ehlmann of the California Institute of Technology and NASA Jet Propulsion
Laboratory, both in Pasadena. “Even if you combined all known carbon
reservoirs together, it is still nowhere near enough to sequester the thick
atmosphere that has been proposed for the time when there were rivers flowing
on the Martian surface.”

Carbon dioxide makes up most of the Martian atmosphere. That
gas can be pulled out of the air and sequestered or pulled into the ground by
chemical reactions with rocks to form carbonate minerals. Years before the
series of successful Mars missions, many scientists expected to find large
Martian deposits of carbonates holding much of the carbon from the planet’s
original atmosphere. Instead, these missions have found low concentrations of
carbonate distributed widely, and only a few concentrated deposits. By far the
largest known carbonate-rich deposit on Mars covers an area at least the size
of Delaware, and maybe as large as Arizona, in a region called Nili Fossae.

Christopher Edwards, a former Caltech researcher now with
the U.S. Geological Survey in Flagstaff, Arizona, and Ehlmann reported the
findings and analysis in a paper posted online by the journal Geology. Their
estimate of how much carbon is locked into the Nili Fossae carbonate deposit
uses observations from numerous Mars missions, including the Thermal Emission
Spectrometer (TES) on NASA’s Mars Global Surveyor orbiter, the mineral-mapping
Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) and two telescopic
cameras on NASA’s Mars Reconnaissance Orbiter, and the Thermal Emission Imaging
System (THEMIS) on NASA’s Mars Odyssey orbiter.

Edwards and Ehlmann compare their tally of sequestered
carbon at Nili Fossae to what would be needed to account for an early Mars
atmosphere dense enough to sustain surface waters during the period when
flowing rivers left their mark by cutting extensive river-valley networks. By
their estimate, it would require more than 35 carbonate deposits the size of
the one examined at Nili Fossae. They deem it unlikely that so many large
deposits have been overlooked in numerous detailed orbiter surveys of the
planet. While deposits from an even earlier time in Mars history could be
deeper and better hidden, they don’t help solve the thin-atmosphere conundrum
at the time the river-cut valleys formed.

The modern Martian atmosphere is too tenuous for liquid
water to persist on the surface. A denser atmosphere on ancient Mars could have
kept water from immediately evaporating. It could also have allowed parts of
the planet to be warm enough to keep liquid water from freezing. But if the
atmosphere was once thicker, what happened to it? One possible explanation is
that Mars did have a much denser atmosphere during its flowing-rivers period,
and then lost most of it to outer space from the top of the atmosphere, rather
than by sequestration in minerals.

“Maybe the atmosphere wasn’t so thick by the time of
valley network formation,” Edwards said. “Instead of Mars that was
wet and warm, maybe it was cold and wet with an atmosphere that had already
thinned. How warm would it need to have been for the valleys to form? Not very.
In most locations, you could have had snow and ice instead of rain. You just
have to nudge above the freezing point to get water to thaw and flow
occasionally, and that doesn’t require very much atmosphere.”

NASA’s Curiosity Mars rover mission has found evidence of ancient
top-of-atmosphere loss, based on the modern Mars atmosphere’s ratio of heavier
carbon to lighter carbon. Uncertainty remains about how much of that loss
occurred before the period of valley formation; much may have happened earlier.
NASA’s MAVEN orbiter, examining the outer atmosphere of Mars since late 2014,
may help reduce that uncertainty.

Arizona State University, Tempe, provided the TES and THEMIS
instruments. The Johns Hopkins University Applied Physics Laboratory, Laurel,
Maryland., provided CRISM. JPL, a division of Caltech, manages the Mars
Reconnaissance Orbiter and Mars Odyssey project for NASA’s Science Mission
Directorate, Washington, and managed the Mars Global Surveyor project through
its nine years of orbiter operations at Mars. Lockheed Martin Space Systems in
Denver built the three orbiters.

For more information about the Mars Reconnaissance Orbiter
mission, visit:

For more information about the Mars Odyssey mission, visit:

Story Source:

The above post is reprinted from materials provided by
NASA/Jet Propulsion Laboratory. Note: Materials may be edited for content and
length.

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Oxygen oasis in Antarctic lake reflects Earth in distant past

At the bottom of a frigid Antarctic lake, a thin layer of
green slime is generating a little oasis of oxygen, a team including UC Davis
researchers has found. It’s the first modern replica discovered of conditions
on Earth two and a half billion years ago, before oxygen became common in the
atmosphere. The discovery is reported in a paper in the journal Geology.

The switch from a planet with very little available oxygen
to one with an atmosphere much like today’s was one of the major events in
Earth’s history, and it was all because some bacteria evolved the ability to
photosynthesize. By about 2.4 billion years ago, geochemical records show that
oxygen was present all the way to the upper atmosphere, as ozone.

What is not clear is what happened in between, or how long
the transition – called the Great Oxidation Event – lasted, said Dawn Sumner,
professor and chair of earth and planetary sciences at UC Davis and an author
on the paper. Scientists have speculated that here may have been “oxygen
oases,” local areas where was abundant before it became widespread around
the planet.

The new discovery in Lake Fryxell in the McMurdo Dry Valleys
could be a modern example of such an ancient oxygen oasis, and help geochemists
figure out what to look for in ancient rocks, Sumner said.

Lake Fryxell. Credit: Tyler Mackey, UC Davis 

Sumner and collaborators including Ian Hawes of the
University of Canterbury, New Zealand have been studying life in these
ice-covered lakes for several years. The microbes that survive in these remote
and harsh environments are likely similar to the first forms of life to appear
on Earth, and perhaps on other planets.

The discovery occurred “a little by accident,”
Sumner said. Hawes and Tyler Mackey, a UC Davis graduate student working with
Sumner, were helping out another research team by diving in Lake Fryxell. The
lakes of the Dry Valleys typically contain oxygen in their upper layers, but
are usually anoxic further down, Sumner said. Lake Fryxell is unusual because
it becomes anoxic at a depth where light can still penetrate.

During their dives below the oxygen zone, Hawes and Mackey
noticed some bright green bacteria that looked like they could be
photosynthesizing. They took measurements and found a thin layer of oxygen,
just one or two millimeters thick, being generated by the bacteria.

Something similar could have been happening billions of
years ago, Sumner said.

“The thought is, that the lakes and rivers were anoxic,
but there was light available, and little bits of oxygen could accumulate in
the mats,” she said.

The researchers now want to know more about the chemical
reactions between the “oxygen oasis” and the anoxic water immediately
above it and sediments below. Is the oxygen absorbed? What reactions occur with
minerals in the water?

Understanding how this oxygen oasis reacts with the environment
around it could help identify chemical signatures preserved in rocks.
Researchers could then go looking for similar signatures in rocks from ancient
lake beds to find “whiffs of oxygen” prior to the Great Oxidation
Event.

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