- Mysterious Giant Plumes Erupt from Mars, and No One Knows Why
- Mars One Chooses 100 Wannabe Martians
- Rosetta Swoops in for the Closest Comet Flyby Yet
- ALMA Sees Super Stellar Nurseries at the Heart of Sculptor Galaxy
|
Posted: 16 Feb 2015 01:54 PM PST
Plumes seen reaching high above the surface of Mars are causing a stir among scientists studying the atmosphere on the Red Planet. On two separate occasions in March and April 2012, amateur astronomers reported definite plume-like features developing on the planet. The plumes were seen rising to altitudes of over 250 km above the same region of Mars on both occasions. By comparison, similar features seen in the past have not exceeded 100 km. “At about 250 km, the division between the atmosphere and outer space is very thin, so the reported plumes are extremely unexpected,” says Agustin Sanchez-Lavega of the Universidad del País Vasco (UPV) in Spain, lead author of the paper reporting the results in the journal Nature.
The features developed in less than 10 hours, covering an area of up to 1000 x 500 km, and remained visible for around 10 days, changing their structure from day to day.
None of the spacecraft orbiting Mars saw the features because of their viewing geometries and illumination conditions at the time.
However, checking archived Hubble Space Telescope images taken between 1995 and 1999 and of databases of amateur images spanning 2001 to 2014 revealed occasional clouds at the limb of Mars, albeit usually only up to 100 km in altitude.
But one set of Hubble images from 17 May 1997 revealed an abnormally high plume, similar to that spotted by the amateur astronomers in 2012.
Scientists are now working on determining the nature and cause of the plumes by using the Hubble data in combination with the images taken by amateurs.
“One idea we’ve discussed is that the features are caused by a reflective cloud of water-ice, carbon dioxide-ice or dust particles, but this would require exceptional deviations from standard atmospheric circulation models to explain cloud formations at such high altitudes,” says Sanchez-Lavega.
“Another idea is that they are related to an auroral emission, and indeed auroras have been previously observed at these locations, linked to a known region on the surface where there is a large anomaly in the crustal magnetic field,” adds Antonio Garcia Munoz, a research fellow at ESA’s ESTEC and co-author of the study.
"Both hypotheses, even if they are the most plausible ones, seem impossible insofar as they challenge our current knowledge about the Martian atmosphere," Sanchez-Lavega concludes.
The jury is still out on the nature and genesis of these curious high-altitude martian plumes. Further insights should be possible following the arrival of ESA’s ExoMars Trace Gas Orbiter at the Red Planet, scheduled for launch in 2016.
The UPV/EHU's Planetary Sciences Group is part of the system of consolidated groups of the Government of the Basque Autonomous Community (region) and has funding from the Spanish Ministry of Economy and Competitiveness. It forms an Associated Unit with the Institute of Astrophysics of Andalusia-CSIC (Spanish National Research Council) and promotes the Master's degree in Space Science and Technology that is run at the Aula EspaZio Gela (room) of the Faculty of Engineering in Bilbao.
 | ||
|
Posted: 16 Feb 2015 01:02 PM PST
From the initial 202,586 applicants, only 100 hopefuls have been selected to proceed to the next round of the Mars One Astronaut Selection Process. These candidates are one step closer to becoming the first humans on Mars. “The large cut in candidates is an important step towards finding out who has the right stuff to go to Mars,” said Bas Lansdorp, Co-founder & CEO of Mars One. “These aspiring martians provide the world with a glimpse into who the modern day explorers will be.”
The Mars 100 Round Three candidates were selected from a pool of 660 candidates after participating in personal online interviews with Norbert Kraft, M.D., Chief Medical Officer. During the interviews the candidates had a chance to show their understanding of the risks involved, team spirit and their motivation to be part of this life changing expedition. “We were impressed with how many strong candidates participated in the interview round, which made it a very difficult selection” said Dr. Norbert Kraft.
There are 50 men and 50 women who successfully passed the second round. The candidates come from all around the world, namely 39 from the Americas, 31 from Europe, 16 from Asia, 7 from Africa, and 7 from Oceania. The complete list of Mars One candidates can be found here: Mars One Round Three Candidates.
The following selection rounds will focus on composing teams that can endure all the hardships of a permanent settlement on Mars. The candidates will receive their first shot at training in the copy of the Mars Outpost on Earth and will demonstrate their suitability to perform well in a team. “Being one of the best individual candidates does not automatically make you the greatest team player, so I look forward to seeing how the candidates progress and work together in the upcoming challenges.” said Dr. Norbert Kraft.
Candidates that were not selected to continue will have a chance to reapply in a new application round that will open in 2015. New application opportunities will follow in order to train candidates that can replace eliminated teams and join the crews of settlers that will leave Earth to live on Mars.
Credit: mars-one.com
 | ||
|
Posted: 16 Feb 2015 11:17 AM PST
On 14 February 2015, ESA's Rosetta spacecraft swooped over the surface of Comet 67P/Churyumov–Gerasimenko at a distance of just 6 km. The closest approach took place at 12:41 GMT over a region known as Imhotep, which is on the larger of the comet’s two lobes. The image reveals the contrasting terrains seen on this comet. Layered and fractured exposed surfaces contrast against expanses of smooth, dust-covered terrain. In some places, such as to the lower right of this image, the faint outline of raised near-circular objects with smooth surfaces can be seen. Elsewhere, boulders ranging in size from a few metres to a few tens of metres are scattered across the surface. The largest boulder, seen to the upper right, is named Cheops.
As well as providing the opportunity to take close-up high-resolution images of the surface, flybys like this also allow Rosetta’s instruments to sample the innermost parts of the comet’s atmosphere, or coma, to understand the connection between the source of the observed activity and the wider coma.
The spacecraft has now begun a new phase of observations, whereby it will continue to fly past at a range of distances, typically between about 15 km and 100 km.
The more distant flybys will provide the broader context of a wide-angle view of the nucleus and its growing coma as the comet moves towards perihelion – the closest approach to the Sun along its orbit. Rosetta is today 345 million kilometres from the Sun; at perihelion, on 13 August this year, it will be at about 186 million kilometres, between the orbits of Earth and Mars.
The image presented here was taken with the navigation camera shortly after closest approach, at 14:19 GMT, from a distance of 8.7 km. It has a scale of 0.74 m/pixel and measures 0.76 km across.
Credit: ESA
 | ||
|
Posted: 16 Feb 2015 09:35 AM PST
Starburst galaxies transmute gas into new stars at a dizzying pace – up to 1,000 times faster than typical spiral galaxies like the Milky Way. To help understand why some galaxies "burst" while others do not, an international team of astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) to dissect a cluster of star-forming clouds at the heart of NGC 253, one of the nearest starburst galaxies to the Milky Way. "All stars form in dense clouds of dust and gas," said Adam Leroy, an astronomer formerly with the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia, and now with The Ohio State University in Columbus. "Until now, however, scientists struggled to see exactly what was going on inside starburst galaxies that distinguished them from other star-forming regions."
ALMA changes that by offering the power to resolve individual star-forming structures, even in distant systems. As an early demonstration of this capability, Leroy and his colleagues mapped the distributions and motions of multiple molecules in clouds at the core of NGC 253, also known as the Sculptor Galaxy.
Sculptor, a disk-shape galaxy currently undergoing intense starburst, is located approximately 11.5 million light-years from Earth, which is remarkably nearby for such an energetic star factory. This proximity makes Sculptor an excellent target for detailed study.
“There is a class of galaxies and parts of galaxies, we call them starbursts, where we know that gas is just plain better at forming stars,” noted Leroy. “To understand why, we took one of the nearest such regions and pulled it apart – layer by layer – to see what makes the gas in these places so much more efficient at star formation.”
ALMA’s exceptional resolution and sensitivity allowed the researchers to first identify ten distinct stellar nurseries inside the heart of Sculptor, something that was remarkably hard to accomplish with earlier telescopes, which blurred the different regions together.
The team then mapped the distribution of about 40 millimeter-wavelength “signatures” from different molecules inside the center of the galaxy. This was critically important since different molecules correspond to different conditions in and around star-forming clouds. For example, carbon monoxide (CO) corresponds to massive envelopes of less dense gas that surround stellar nurseries. Other molecules, like hydrogen cyanide (HCN), reveal dense areas of active star formation. Still rarer molecules, like H13CN and H13CO+, indicate even denser regions.
By comparing the concentration, distribution, and motion of these molecules, the researchers were able to peel apart the star-forming clouds in Sculptor, revealing that they are much more massive, ten times denser, and far more turbulent than similar clouds in normal spiral galaxies.
These stark differences suggest that it’s not just the number of stellar nurseries that sets the throttle for a galaxy to create new stars, but also what kind of stellar nurseries are present. Because the star-forming clouds in Sculptor pack so much material into such a small space, they are simply better at forming stars than the clouds in a galaxy like the Milky Way. Starburst galaxies, therefore, show real physical changes in the star-formation process, not just a one-to-one scaling of star formation with the available reservoir of material.
“These differences have wide-ranging implications for how galaxies grow and evolve,” concluded Leroy. “What we would ultimately like to know is whether a starburst like Sculptor produces not just more stars, but different types of stars than a galaxy like the Milky Way. ALMA is bringing us much closer to that goal.”
These results are accepted for publication in the Astrophysical Journal and were presented February 15, 2015, at a news conference at the American Association for the Advancement of Science (AAAS) meeting in San Jose, California.
Credit: nrao.edu
|
댓글 없음:
댓글 쓰기