Posted on by Nancy Atkinson

Winds on Venus are Variable, Cyclical

Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA/ Universidad del País Vasco (R.Hueso)

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The Venus Express spacecraft has been continuously monitoring the planet in orbit since 2006, and scientists now have enough data to start building a complete picture of the planet’s atmospheric phenomena. They have put together a 3-D picture of Venusian winds for the southern hemisphere. It was known that the winds on Venus are extremely fast and powerful, but what was not known was their extreme variability. The winds are highly influenced by the sun, as well as an unusual and unknown mechanism that seems to re-set itself every five days.

The Venus Express Visual and Infrared Thermal Imaging Spectrometer, VIRTIS, has been studying the thick blanket of clouds that surround Venus, gathering data on the winds. The area studied spans altitudes of 45 to 70 km above the surface and covers the entire southern hemisphere, up to the equator. It is above the southern hemisphere that Venus Express reaches its highest point in orbit (about 66 000 km), allowing the instruments to obtain a global view.

Agustin Sánchez-Lavega, from the Universidad del País Vasco in Bilbao, Spain, led the research on 3-D wind mapping with data from the first year of VIRTIS observations. “We focused on the clouds and their movement. Tracking them for long periods of time gives us a precise idea of the speed of the winds that make the clouds move and of the variation in the winds,” he said.

The spacecraft has the ability to peer through Venus’s thick atmospheric layers and obtain a truly global picture. The scientists tracked three atmospheric layers and followed the movement of hundreds of clouds in each layer.

In total, the team tracked 625 clouds at about 66 km altitude, 662 at around 61 km altitude, and 932 at about 45-47 km altitude, on the day and night sides of the planet. The individual cloud layers were imaged over several months for about 1-2 hours each time.

“We have learnt that between the equator and 50-55˚ latitude south, the speed of the winds varies a lot, from about 370 km/h at a height of 66 km down to about 210 km/h at 45-47 km”, said Sánchez-Lavega.

“At latitudes higher than 65Ëš, the situation changes dramatically – the huge hurricane-like vortex structure present over the poles takes over. All cloud levels are pushed on average by winds of the same speed, independently of the height, and their speed drops to almost zero at the centre of the vortex.”

Layers of Venus' winds. Credits: R. Hueso (Universidad del País Vasco)
Layers of Venus' winds. Credits: R. Hueso (Universidad del País Vasco)

Sánchez-Lavega and colleagues observed that the speed of the zonal winds (which blow parallel to the lines of latitude) strongly depend on the local time. The difference in the Sun’s heat reaching Venus in the mornings and in the evenings – called the solar tide effect – influences the atmospheric dynamics greatly, making winds blow more strongly in the evenings.

Most unusual was the finding that, on average, the winds regain their original speeds every five days. But the mechanism that produces this periodicity needs further investigation. VIRTIS will continue its observations in an effort to understand the mechanism, as well as getting more precise readings on the variability of the Venusian winds.

Source: ESA

Posted on by Nancy Atkinson

Where In the Universe Challenge #21

Here’s this week’s image for the “Where In The Universe” challenge. Take a look at the image above and guess where in our universe this image was taken. Extra points if you can name the spacecraft responsible for the image as well. No peeking below before you make your guess. Ready? You may begin….


This is an image of Earth’s Moon, taken by the Japanese Kaguya spacecraft, currently in orbit of the Moon. Interestingly, this image shows the Apollo 17 landing site at the Taurus-Littrow Valley, located on the southeastern rim of Mare Serenitatis. A flat valley is surrounded by mountains which were made of ejecta rocks from the when this “sea” was created by an asteroid impact. Since Kaguya is in a polar orbit of the moon, this image looks down from the south to the north. The spacecraft’s Terrain Camera was used to create this 3-D-like image.

See more images from Kaguya here. There’s quite a bit of information included with each image. The resolution isn’t high enough to see any features from the Apollo spacecraft, however the red circle in the Terrain Camera image below encircles the potential “halo” by Apollo 17 lunar module “Challenger” engine exhaust plume.

Possible Apollo 17 halo of exhaust. Credit: Kaguya
Possible Apollo 17 halo of exhaust. Credit: Kaguya

How did you do?

Posted on by Nancy Atkinson

Super-massive and Small Black Holes Both Suck

Artist's impression of material falling into a super-massive black hole together with the average shape of the periodic X-ray signal from REJ1034+396. Credit: Aurore Simonnet, Sonoma State University

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Sorry, couldn’t resist that title. Astronomers studying black holes are able to “see” them due to the fact that the gas getting sucked in gets extremely hot and emits X-rays. These X-ray pulses are commonly seen among smaller black holes, but until now, had not been detected from super-massive black holes. But astronomers using the XMM Newton X-ray satellite have discovered a strong X-ray pulse emitting from a giant black hole in a galaxy 500 million light years from Earth, created by gas being sucked in by gravity. “Scientists have been looking for such behaviour for the past 20 years and our discovery helps us begin to understand more about the activity around such black holes as they grow,” said Dr. Marek Gierlinski from Durham University. Gierlinski and his colleagues say this finding is the “missing link” between small and super-massive black holes.

The astronomers were looking at the center of the galaxy REJ1034+396 galaxy and found that X-rays are being emitted as a regular signal from the super-massive black hole. They say the frequency of the pulse is related to the size of the black hole. “Such signals are a well known feature of smaller black holes in our Galaxy when gas is pulled from a companion star,” said Gierlinski. “The really interesting thing is that we have now established a link between these light-weight black holes and those millions of times as heavy as our Sun.”

The scientists hope future research will tell them why some super-massive black holes show this behavior while others do not. Most galaxies, including the Milky Way, are believed to contain super-massive black holes at their centers.

The researchers, who publish their findings in the journal Nature on September 18, say their discovery will increase the understanding of how gas behaves before falling on to a black hole as it feeds and develops.

Source: Durham University

Posted on by Nancy Atkinson

Phoenix Lander Working Hard Before Summer’s End on Mars

The Phoenix Mars Lander is working as fast as it can to dig and deliver as many samples as possible before the power produced by Phoenix’s solar panels declines due to the end of the Martian summer. This image, from Sol 107 (Sept. 12 here on Earth), shows the lander has delivered a sample of soil from the “Snow White” trench to the Wet Chemistry Laboratory. A small pile of soil is visible on the lower edge of the second cell from the top. This deck-mounted lab is part of Phoenix’s Microscopy, Electrochemistry and Conductivity Analyzer (MECA).

The Wet Chemistry Laboratory mixes Martian soil with an water-based solution from Earth as part of a process to identify soluble nutrients and other chemicals in the soil. Preliminary analysis of this soil confirms that it is alkaline, and composed of salts and other chemicals such as perchlorate, sodium, magnesium, chloride and potassium. This data validates prior results from that same location, said Michael Hecht of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., the lead scientist for MECA.

In the coming days, the Phoenix team will also fill the final four of eight single-use ovens on another soil-analysis instrument, the Thermal and Evolved Gas Analyzer, or TEGA.

Source: Phoenix news site

Posted on by Nancy Atkinson

Hubble NICMOS Instrument Experiences Anomaly

NICMOS

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A cooling system for the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) science instrument aboard the Hubble telescope experienced an anomaly during a restart, causing the instrument to go into safe mode. After a couple of additional restarts, the problem still persists, and a decision was made for NICMOS to “stand down” while engineers study the anomaly and allow the cooling system to warm up, which may take a couple of weeks. In the short term, this will affect planned science observations, and engineers are hoping to avoid any long term complications. At this point, if the problem cannot be fixed from the ground, it is unclear how it might affect the upcoming servicing mission, scheduled for an Oct. 10 launch.

New software was uploaded last week to the computer that controls Hubble’s five science instruments to get the telescope ready for the upcoming servicing mission (SM4). Installation of the software requires putting all of the telescope’s science instruments into safe mode configuration for a short period of time.

About six hours after the system was reactivated, at about 4 a.m. EDT on Sept. 11, the NICMOS anomaly was seen. The cooling system put itself into safe mode after seeing too high a speed in the circulator pump operation. After studying data, flight controllers modified operating protection parameters and attempted a restart of the system on Sunday, Sept. 14. The circulator system again indicated a high speed violation so the system was returned to safe mode.

Engineers believe the ice particles in the cooling loop could be causing the problem. With some small adjustments in start-up procedures, engineers think the cooling system can be successfully reactivated. The flight team tried another restart Monday evening (9/15). The anomaly was still seen after that restart, so the Hubble Project’s plan now is to stand down from any additional attempts to restart. Engineers will study the anomaly while waiting until the cooling system has been allowed to warm somewhat, which may take several weeks.

The impact to planned NICMOS science operations involves approximately 70 exposures from three guest observer programs and additional exposures from two NICMOS internal calibration programs. Additionally, all NICMOS science has been removed from this week’s observation schedule. Sixty-one orbits of NICMOS science were scheduled for the week between September 15 and September 21.

The servicing mission already has a jam-packed schedule, and its uncertain if any last minute additions to the mission would be possible.

Source: NASA

Posted on by Nancy Atkinson

Do All Galaxies Have Tentacles?

This Hubble Space Telescope image of two spiral galaxies shows an interesting feature on the smaller galaxy. Silhouetted in front of the larger background galaxy is a small galaxy, and tentacles of dust can be seen extending beyond the small galaxy’s disk of starlight. These dark, dusty structures appear to be devoid of stars, almost like barren branches. They are rarely so visible in a galaxy because there is usually nothing behind them but darkness. But here, with the backdrop of the larger galaxy they are illuminated. Astronomers have never seen dust this far beyond the visible edge of a galaxy, and they don’t know if these dusty structures are common features in galaxies.

The background galaxy is 780 million light-years away, but the distance between the two galaxies has not yet been calculated. Astronomers think the two are relatively close, but not close enough to actually interact. The background galaxy is about the size of the Milky Way Galaxy and is about 10 times larger than the foreground galaxy. Understanding a galaxy’s color and how dust affects and dims that color are crucial to measuring a galaxy’s true brightness. By knowing the true brightness, astronomers can calculate the galaxy’s distance from Earth.

Most of the stars speckled across this image belong to the nearby spiral galaxy NGC 253, which is out of view to the right. Astronomers used Hubble’s Advanced Camera for Surveys to snap images of NGC 253 when they spied the two galaxies in the background. From ground-based telescopes, the two galaxies look like a single blob. But the Advanced Camera’s sharp “eye” distinguished the blob as two galaxies, cataloged as 2MASX J00482185-2507365. The images were taken on Sept. 19, 2006.

Source: Hubblesite

Posted on by Nancy Atkinson

Our Sun May Have Migrated Over Time

Computer simulation showing the development and evolution of the disk of a galaxy such as the Milky Way. Credit: Rok Roškar

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When you stir cream in your coffee or tea, does the swirl stay the same or does it change as it spins in your cup? As galaxies form and swirl, the motions and eddies may actually cause stars to move within the galaxy. A long-standing scientific belief holds that stars tend to hang out in the same general part of a galaxy where they originally formed. But some astrophysicists have recently questioned whether that is true, and now new simulations show that, at least in galaxies similar to our own Milky Way, stars such as the sun can migrate great distances. If this is true, it could change the entire notion that there are parts of galaxies – so-called habitable zones – that are more conducive to supporting life than other areas.

“Our view of the extent of the habitable zone is based in part on the idea that certain chemical elements necessary for life are available in some parts of a galaxy’s disk but not others,” said Rok RoÅ¡kar, a doctoral student in astronomy at the University of Washington. “If stars migrate, then that zone can’t be a stationary place.”

RoÅ¡kar is lead author of a paper describing the findings from the simulations, published in the Sept. 10 edition of the Astrophysical Journal Letters. If the idea of habitable zone doesn’t hold up, it would change scientists’ understanding of just where, and how, life could evolve in a galaxy, he said.

Using more than 100,000 hours of computer time on a UW computer cluster and a supercomputer at the University of Texas, the scientists ran simulations of the formation and evolution of a galaxy disk from material that had swirled together 4 billion years after the big bang. Watch a simulation video.

The simulations begin with conditions about 9 billion years ago, after material for the disk of our galaxy had largely come together but the actual disk formation had not yet started. The scientists set basic parameters to mimic the development of the Milky Way to that point, but then let the simulated galaxy evolve on its own.

If a star, during its orbit around the center of the galaxy, is intercepted by a spiral arm of the galaxy, scientists previously assumed the star’s orbit would become more erratic in the same way that a car’s wheel might become wobbly after it hits a pothole.

However, in the new simulations the orbits of some stars might get larger or smaller but still remain very circular after hitting the massive spiral wave. Our sun has a nearly circular orbit, so the findings mean that when it formed 4.59 billion years ago (about 50 million years before the Earth), it could have been either nearer to or farther from the center of the galaxy, rather than halfway toward the outer edge where it is now.

Migrating stars also help explain a long-standing problem in the chemical mix of stars in the neighborhood of our solar system, which has long been known to be more mixed and diluted than would be expected if stars spent their entire lives where they were born. By bringing in stars from very different starting locations, the sun’s neighborhood has become a more diverse and interesting place, the researchers said.

The findings are based on a few runs of the simulations, but the scientists plan to run a range of simulations with varying physical properties to generate different kinds of galactic disks, and then determine whether stars show similar ability to migrate large distances within different types of disk galaxies.

Source: University of Washington

Posted on by Nancy Atkinson

Dark Matter Halos? How About Disks, Too

A composite image shows a dark matter disk in red. From images in the Two Micron All Sky Survey. Credit: Credit: J. Read & O. Agertz.

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Scientists are trying to understand the invisible and hypothetical ‘dark matter’ – the stuff that we know exists by inference of its gravitational influence on the matter we can see. The most common held notion of dark matter is that it exists in ‘halos’ or clumps that surround galaxies. But a new study predicts that galaxies like our own Milky Way, also contain a disk of dark matter. Using the results of a supercomputer simulation, scientists from the University of Zurich and the University of Central Lancashire say that if dark matter in fact resides as a disk within a galaxy, it could allow physicists to directly detect and identify the nature of dark matter for the first time.

Physicists believe dark matter makes up 22% of the mass of the Universe (compared with the 4% of normal matter and 74% comprising the mysterious ‘dark energy’). But, despite its pervasive influence, no-one is sure what dark matter consists of.

This ‘standard’ theory of dark matter is based on supercomputer simulations that model the gravitational influence of the dark matter alone. The new work includes the gravitational influence of the stars and gas that also make up our Galaxy.

Stars and gas are thought to have settled into disks very early on in the life of the Universe and this affected how smaller dark matter halos formed. The team’s results suggest that most lumps of dark matter in our locality merged to form a halo around the Milky Way. But the largest lumps were preferentially dragged towards the galactic disk and were then torn apart, creating a disk of dark matter within our Galaxy.

“The dark disk only has about half of the density of the dark matter halo, which is why no one has spotted it before,” said lead author Justin Read. “However, despite its low density, if the disk exists it has dramatic implications for the detection of dark matter here on Earth.”

The Earth and Sun move at some 220 kilometres per second along a nearly circular orbit about the center of our Galaxy. Since the dark matter halo does not rotate, from an Earth-based perspective it feels as if we have a ‘wind’ of dark matter flowing towards us at great speed. By contrast, the ‘wind’ from the dark disk is much slower than from the halo because the disk co-rotates with the Earth.

“It’s like sitting in your car on the highway moving at a hundred kilometres an hour”, said team member Dr. Victor Debattista. “It feels like all of the other cars are stationary because they are moving at the same speed.”

This abundance of low-speed dark matter particles, the science team says, could be a real boon for researchers because they are more likely to excite a response in dark matter detectors than fast-moving particles. “Current detectors cannot distinguish these slow moving particles from other background ‘noise’,” said Prof. Laura Baudis, a collaborator at the University of Zurich and one of the lead investigators for the XENON direct detection experiment, which is located at the Gran Sasso Underground Laboratory in Italy. “But the XENON100 detector that we are turning on right now is much more sensitive. For many popular dark matter particle candidates, it will be able to see something if it’s there.”

If so, its possible that the dark disk could be directly detected in the very near future.

Sources: Monthly Notices paper, Royal Astronomical Society

Posted on by Nancy Atkinson

Newest Mission to Mars: MAVEN

Why do planets like Mars have a different atmosphere than Earth? Credit: NASA

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Did Mars once have a thick atmosphere? Could the climate on the Red Planet have supported water and possibly life in the past? These are the questions NASA hopes to answer in great detail with the newest orbiter mission to Mars. Called the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, the $485 million mission is scheduled for launch in late 2013. MAVEN is part of the Mars Scout Program, which is designed to send a series of small, low-cost, principal investigator-led missions to the Red Planet. The Phoenix Mars Lander was the first spacecraft selected in this program. “This mission will provide the first direct measurements ever taken to address key scientific questions about Mars’ evolution,” said Doug McCuistion, director of the Mars Exploration Program at NASA Headquarters in Washington.

Evidence from orbit and the planet’s surface points to a once denser atmosphere on Mars that supported the presence of liquid water on the surface. As part of a dramatic climate change, most of the Martian atmosphere was lost. MAVEN will make definitive scientific measurements of present-day atmospheric loss that will offer clues about the planet’s history.

“The loss of Mars’ atmosphere has been an ongoing mystery,” McCuistion said. “MAVEN will help us solve it.”

The science team will be led from the University of Colorado at Boulder, and its Laboratory for Atmospheric and Space Physics. The principal investigator for the mission is Bruce Jakosky from UC Boulder. “We are absolutely thrilled about this announcement,” said Jakosky. “We have an outstanding mission that will obtain fundamental science results for Mars. We have a great team and we are ready to go.”

Artist depiction of the MAVEN spacecraft. Credit: NASA
Artist depiction of the MAVEN spacecraft. Credit: NASA

Lockheed Martin of Littleton, Colo., will build the spacecraft based on designs from NASA’s Mars Reconnaissance Orbiter and 2001 Mars Odyssey missions.
MAVEN was evaluated to have the best science value and lowest implementation risk from 20 mission investigation proposals submitted in response to a NASA Announcement of Opportunity in August 2006.

After arriving at Mars in the fall of 2014, MAVEN will use its propulsion system to enter an elliptical orbit ranging 90 to 3,870 miles above the planet. The spacecraft’s eight science instruments will take measurements during a full Earth year, which is roughly equivalent to half of a Martian year.
MAVEN’s instrument suites include a remote sensing package that will determine global characteristics of the upper atmosphere, and the spacecraft will dip to an altitude of 80 miles above the planet. A particles and fields payload contains six instruments that will characterize the solar wind, upper atmosphere and the ionosphere – a layer of charged particles very high in the Martian atmosphere.

The third instrument suite, a Neutral Gas and Ion Mass Spectrometer will measure the composition and isotopes of neutral and charged forms of gases in the Martian atmosphere

During and after its primary science mission, the spacecraft may be used to provide communications relay support for robotic missions on the Martian surface.

More information on MAVEN.

Sources: NASA, UC Boulder

Posted on by Nancy Atkinson

NASA Weathers Hurricane; May Impact Hubble Mission

Trees down on a street in Houston, Texas. Credit: Houston Chronicle, DJ Sherm

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NASA’s Johnson Space Center in Houston weathered Hurricane Ike fairly well, but damage to some buildings, including the roof of the Mission Control Center will need to be repaired before the facility is ready to open for normal operations. A space agency spokesman said it could be late this week or even sometime during the week of Sept. 21 before all the buildings would reopen. The 16,500 employees at JSC will also need to access and repair any damage to their own homes as well. JSC lost power, but essential systems were powered with generators. Controller for the International Space Station established a temporary control center at a hotel inland in Austin, Texas before Johnson was closed on Thursday. Working with another team at NASA’s Marshall Space Flight Center in Huntsville, Alabama, controllers are trying to fill in until Mission Control can re-open.

While there was some standing water, JSC was not affected by Ike’s Galveston Bay surge, but high winds caused roof damage and downed trees. Repairs and cleanup were under way on Sunday.
Meanwhile, the space agency has not assessed the impact of the storm on plans for the scheduled October 10 launch of the shuttle Atlantis on a mission to overhaul the Hubble Space Telescope and the November 12 date for launching shuttle Endeavour on a space station assembly mission, said David Waters, spokesman for United Space Alliance, NASA’s shuttle prime contractor.

Additionally, a resupply ship’s docking with the ISS was delayed, and it waits on orbit near the station. U.S. and Russian flight controllers hope to dock the unmanned Progress supply ship Wednesday at 2:43 p.m. EDT. The cargo craft was launched from the Baikonur Cosmodrome in Kazakhstan last Wednesday and originally was scheduled to dock Friday.

Sources: Houston Chronicle, Spaceflightnow.com