Wednesday, October 17, 2007

China counts down to man on moon


China launches its first lunar orbiter next week as it counts down to putting a man on the moon within 15 years, state media said on Wednesday.

Advanced cameras and x-ray "spectrometers" have been installed on the orbiter, the Chang'e One, for mapping 3D images of the moon's surface and analyzing moon dust, Xinhua news agency said.

The next step in the program is to launch a moon vehicle, and bring it back to Earth, and to put a man on the moon "within 15 years", the China Daily said.

"We have taken hundreds of preventative measures directed towards a successful launch," Zhang Qingwei, minister in charge of the Commission of Science, Technology and Industry for National Defense, told reporters.

Zhang said the probe had already been transported to the launch site in Xichang in the southwestern province of Sichuan.

"Although the risks are great, we have confidence it will be a success."

The launch is set for next Wednesday, a date chosen "with the consideration of weather and celestial conditions", Zhang said.

China's space exploration program has come far since late leader Mao Zedong lamented that China could not even launch a potato into space.

In 2003, it became only the third country after the former Soviet Union and the United States to launch a man into space aboard its own rocket. In October 2005, it sent two men into orbit and plans a space walk by 2008.

But China's space plans have faced increasing international scrutiny. Fears of a potential space arms race with the United States and other powers have mounted since it blew up one of its own weather satellites using a ground-based missile in January.

Japan plans to launch its first mission to land a spacecraft on the moon in the next decade -- a feat so far achieved only by the former Soviet Union and the United States.


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Hubble Shows 'Baby' Galaxy Is Not So Young After All


The NASA/ESA Hubble Space Telescope has found out the true nature of a dwarf galaxy that astronomers had for a long time identified as one of the youngest galaxies in the Universe. Astronomers using the NASA/ESA Hubble Space Telescope have made observations of the galaxy I Zwicky 18 which seem to indicate that it is in fact much older and much farther away than previously thought.

Observations of I Zwicky 18 at the Palomar Observatory around 40 years ago seemed to show that it was one of the youngest galaxies in the nearby Universe. The studies suggested that the galaxy had erupted with star formation billions of years after its galactic neighbours, like our galaxy the Milky Way. Back then it was an important finding for astronomers, since this young galaxy was also nearby and could be studied in great detail; something that is not possible with observations made across great distances when the universe was much younger.

But these new Hubble data have quashed that possibility. The telescope found fainter older red stars contained within the galaxy, suggesting its star formation started at least one billion years ago and possibly as much as 10 billion years ago. The galaxy, therefore, may have formed at the same time as most other galaxies.

“Although the galaxy is not as youthful as was once believed, it is certainly developmentally challenged and unique in the nearby Universe,” said astronomer Alessandra Aloisi, who led the new study. Spectroscopic observations with ground-based telescopes have shown that I Zwicky 18 is mostly composed of hydrogen and helium, the main ingredients created in the Big Bang. In other words the stars within it have not created the same amounts of heavier elements as seen in other galaxies nearby.

Thus the galaxy’s primordial makeup suggests that its rate of star formation has been much lower than that of other galaxies of similar age. The galaxy has been studied with most of NASA’s telescopes, including the Spitzer Space Telescope, the Chandra X-ray Observatory, and the Far Ultraviolet Spectroscopic Explorer (FUSE). However, it remains an outstanding mystery why I Zwicky 18 formed so few stars in the past, and why it is forming so many new stars right now.

The new Hubble data also suggest that I Zwicky 18 is 59 million light-years from Earth, almost 10 million light-years more distant than previously believed. On extragalactic standards this is still in our own backyard yet the galaxy’s larger-than-expected distance may now explain why astronomers have had difficulty detecting older, fainter stars within the galaxy until now. In fact, the faint old stars in I Zwicky 18 are almost at the limit of Hubble’s sensitivity and resolution.

Aloisi and her team discerned the new distance by observing blinking stellar distance-markers within I Zwicky 18. These massive stars, called Cepheid variables, pulse with a regular rhythm. The timing of their pulsations is directly related to their brightness. By comparing their actual brightness with their observed brightness, astronomers can precisely measure their distance.

The team determined the observed brightness of three Cepheids and compared it to the actual brightness predicted by theoretical models specifically calculated for the low metal content of I Zwicky 18 in order to determine the galaxy’s distance. The Cepheid distance was also validated through another distance indicator, specifically the observed brightness of the brightest red stars in a characteristic stellar evolutionary phase (the so-called “giant” phase).

Cepheid variable stars have been studied for decades (especially by Hubble) and have been instrumental in the determination of the scale of our universe. This is the first time, however, that variable stars with so few heavy elements were found. This may provide unique new insights into the properties of variable stars, which is now a topic of ongoing study.

Mars Express: Hummocky And Shallow Maunder Crater


The High Resolution Stereo Camera (HRSC) on ESA’s Mars Express orbiter has obtained pictures of the Noachis Terra region on Mars, in particular, the striking Maunder crater.

Maunder crater lies at 50° South and 2° East, approximately in the center of Noachis Terra.

The impact crater, named after the british astronomer Edward W. Maunder (1851-1928), is located halfway between Argyre Planitia and Hellas Planitia on the southern Highlands of Mars.

With a diameter of 90 kilometres and a depth of barely 900 metres, the crater is not one of the largest impact craters on Mars at present, but it used to be much deeper. It has since been filled partially with large amounts of material.

The west of the crater experienced a major slope failure, during which a large landslide transported loose material eastward, to the inner parts of the crater. The edges of the crater rim that collapsed exhibit gullies which might be associated with the mass transport of the material.

The transition zone from the western rim of the crater to the rather smooth crater floor on the eastern edge shows hummocky terrain. Such terrain exhibits small, irregularly-shaped hills and valleys. The hummocky terrain in the Maunder crater was formed by deposition of landslide debris.

In the east, the crater floor is bounded by a trough, approximately 700 metres deep. The trough may be associated with a landslide on the western edge of the crater. Some gullies can be seen on the upper edge of the trough which is possible evidence for water seepage.

The small, 500 to 2500-metre long, dark features on the crater floor are eye-catching. These features are called Barchan dunes, one of the most abundant dune forms in arid environments. Dunes of this kind are also found on Earth, for example in the West-African Namib desert.

The colour scenes have been derived from the three HRSC-colour channels and the nadir channels. The perspective views have been calculated from the digital terrain model derived from the HRSC stereo channels. The anaglyph image was calculated from the nadir channels and two stereo channels, stereoscopic glasses are required for viewing. The 3-D (anaglyph) picture has been put together from several individual 3-D images of different scenes, enhancing the view over larger areas.