|
By Daniel Fischer Every page present in Europe & the U.S.!
| Ahead | Awards 
The latest issue!
| A German companion! (SuW version) Current mission news: MGS (latest pictures!) + Cassini + Galileo + NEAR |
I've started an informal website here with information on the eclipse itself and logistical aspects (mostly about Zambia). It's a mix of English and German, with most links to English-language sites.
| |
Liquid water on today's Mars?MGS images show indirect evidence for flowing water just below the surface in the geological present / What keeps it liquid, remains a mysteryForced by rampant rumors to move a news conference ahead one week, NASA on June 22 announced that images from the Mars Global Surveyor suggest there may be current sources of liquid water at or near the surface of the red planet: The images, which show the smallest details ever observed from martian orbit, contain features comparable to those left by flash floods on Earth. They look like gullies formed by flowing water and the deposits of soil and rocks transported by these flows. The features appear to be so young that they might be forming today - which would be evidence of a ground water supply, similar to an aquifer."For two decades scientists have debated whether liquid water might have existed on the surface of Mars just a few billion years ago," said Dr. Ed Weiler, Associate Administrator for Space Science, NASA Headquarters. "With today's discovery, we're no longer talking about a distant time. The debate has moved to present-day Mars. The presence of liquid water on Mars has profound implications for the question of life not only in the past, but perhaps even today. If life ever did develop there, and if it survives to the present time, then these landforms would be great places to look." The gullies observed in the images are on cliffs - usually in crater or valley walls - and are made up of a deep channel with a collapsed region at its upper end (an "alcove") and at the other end an area of accumulated debris (an "apron") that appears to have been transported down the slope. Relative to the rest of the martian surface, the gullies appear to be extremely young, meaning they may have formed in the recent past. "They could be a few million years old," says MGS imaging leader Mike Malin, "but we cannot rule out that some of them are so recent as to have formed yesterday." Because the atmospheric pressure at the surface of Mars is about 100 times less than it is at sea level on Earth, liquid water would immediately begin to boil explosively when exposed at the martian surface - so how can these gullies form? The process must involve repeated outbursts of water and debris, similar to flash floods on Earth. Here's an idea: When water evaporates it cools the ground - that would cause the water behind the initial seepage site to freeze. This would result in pressure building up behind an 'ice dam.' And ultimately, the dam would break and send a flood down the gully. The occurrence of gullies is quite rare: Only a few hundred locations have been seen in the many tens of thousands of places surveyed by the orbiter camera. Most are in the martian southern hemisphere, but a few are in the north. "What is odd about these gullies is that they occur where you might not expect them - in some of the coldest places on the planet," Malin indicated: "Nearly all occur between latitudes 30 degrees and 70 degrees, and usually on slopes that get the least amount of sunlight during each martian day." The water supply is believed to be about 100 to 400 meters below the surface, and limited to specific regions across the planet. The process that starts the water flowing remains a mystery, but the team believes it is not the result of volcanic heating. Each flow that came down each gully may have had a volume of water of, roughly, 2500 cubic meters. |
| ||||||||
Robot telescope find 70 supernovaeEvery 3rd Ia supernova turns out to be unusualThe world's most successful automated search for nearby supernovae, conducted by the University of California, Berkeley, has found 70 of these exploding stars in its first two years of operation, providing valuable information about the evolution and physics of stellar explosions. The data also are giving cosmologists greater confidence in conclusions about the structure of the universe gleaned from studies of distant supernovae. UC Berkeley's robotic telescope KAIT (Katzman Automatic Imaging Telescope) scans about 1000 galaxies a night looking for new points of light, generally within about 500 million light years of Earth.Because the telescope catches almost every supernova in the galaxies it monitors, the data give astronomers a better idea of how common supernovae are and of their variety. For example it has been found that so-called Type Ia supernovae are less uniform than once thought. This may have major implications, since Type Ia supernovae are used as a "standard candle" to estimate galactic distances. If there are several common types, conclusions based on an assumption of uniformity may be incorrect. According to the KAIT data more than one-third of Type Ia supernovae are peculiar, in that they are brighter or dimmer than the "average" Type Ia, or that their spectra show unusual chemical composition. Perhaps some Type Ia supernovae result from the merger of two white dwarf stars into an unstable mass that quickly explodes, and Type Ia supernovae may be produced in multiple ways? And there are also possible differences between the pattern of brightening of nearby supernovae and the pattern typical of distant supernovae. This is probably not a significant problem for cosmologists who have concluded, from analysis of the distance and recession speed of distant supernovae, that the universal expansion is accelerating. But it is important to verify that supernovae which exploded billions of years ago look the same - in particular, that they have the same peak power output - as those which exploded more recently. |
| ||||||||
Another bunch of Chandra discoverieshas been published in early June at a major astronomy conference:
|
| ||||||||
The XMM-Newton satellite has been sighted visuallyby an amateur astronomer, at 9th mag.: This exploit, using a commercially available 20cm Schmidt-Cassegrain telescope, was achieved by the French amateur astronomer Gerard Faure, who is more accustomed to tracking down asteroids. But the also belongs to the 'Alphonse Pouplier' Internet network for all those who want to observe artificial satellites. Faure tried three times, twice in May, once on 3 June, but unsuccessfully. Once again on the evening of 9 June, after sleeping a couple of hours at his privileged viewing site situated an altitude of 1170m, he was behind his 20 cm Celestron 8 ready to spot the satellite with a magnification of 80 times. "The suspense didn't last long," Faure recalls: "Shortly after 2 am local time, coming down from the south-west, not far from Alpha Ophiuchus, there was XMM-Newton slightly south of the predicted trajectory on my charts! It was particularly bright, at magnitude 9.2, much more than I had expected." |
| ||||||||
"Cat's Eye Nebula" surrounded by concentric rings - what was the dying star thinking?The Cat's Eye Nebula (NGC 6543) has become one of the most famous icons of the Hubble Space Telescope's science program (it made the cover of both of the first two books on the HST's achievements, by Petersen & Brandt and Fischer & Duerbeck) - but now new Hubble data show that this planetary nebula is located centrally in a series of round rings resembling an archery target! The surrounding rings, which were almost certainly ejected before the bright core of the nebula, provide new insights into the preceding history of the star's decline to death prior to the formation of the famous Cat's Eye - a story that could well be a preview of the death tantrums of our Sun in five billion years.Until now the most eye-catching features of the Cat's Eye include its bright colorful, symmetric center or "core", expelled from its central star in an outburst that would have been seen on Earth about the year 1000 A.D. - had anyone been looking. The rings around the Cat's Eye show that this outburst wasn't the first one (though it was almost certainly the most spectacular): Apparently the star had been steadily huffing and puffing, producing a new round bubble of ejected gas every 1500 years or so for the past 20,000 years or more. Each "puff" contains thousands of Earth masses worth of material. The new result shows that the steady pulsations that form each ring are followed by some abrupt change in internal behavior that produces spectacularly well-organized outburst patterns at the very end of their lives - a puzzle and a challenge to long-standing theories of stellar evolution. How can a star well on its way to white-dwarf rigor mortis eject its last and most energetic outburst with such sublime control? Almost all dying stars do this, although in a variety of different lovely patterns. Perhaps the last ejection dredges out a twisted magnetic field which sculpts the gas on its way out, but that's just a guess at this point. |
| ||||||||
New model of Jupiter's interior after lab data shows different behavior of metallic hydrogenPhysicists at the Lawrence Livermore National Laboratory in California have recreated conditions like those inside Jupiter with new laboratory experiments in which a high-power laser generates a shock wave in a metal 'pusher' material that squeezes hydrogen (or rather its heavier isotope deuterium). Like normal metals, metallic hydrogen is expected to reflect light strongly: The researchers found that the reflectance of the deuterium started to increase rapidly even at pressures as low as 0.2 megabars. The metallic state thus starts to appear at much lower pressures than previously thought.And that the change from a non-metal to a metal is not abrupt but gradual. The same thing then should happen in Jupiter: Previous models have pictured the planet's interior as a layered, onion-like structure with sharp boundaries between the insulating and metallic forms of liquid hydrogen - like the boundary between the Earth's rocky mantle and its liquid iron core. The new results indicate that, on the contrary, the metallic form of hydrogen unveils itself gradually over perhaps hundreds or thousands of kilometers. |
| ||||||||
Sunrise for Eros' South PoleLater this week the Sun will rise over the south pole of asteroid Eros, revealing unexplored terrain to the instruments on NASA's NEAR-Shoemaker spacecraft. When it entered orbit around 433 Eros in February, the asteroid was in the middle of northern summer: Eros's north pole was constantly bathed in sunlight while southern regions were in total darkness. The extreme tilt of Eros' rotation axis - at 89 degress it practically lies in the orbital plane - makes for particularly pronounced seasons. Three of NEAR's scientific instruments depend on reflected sunlight to do their jobs, so many of the mission's early results have focused on observations of the space rock's northern parts. Scientists have been waiting expectantly to see more of the asteroid and later this week they will get their wish.On June 25, 2000, the subsolar point on Eros will cross the asteroid's equator heading south. As the Sun rises over Eros's south pole, sunlight will illuminate terrain that's been hidden from view since NEAR went into orbit four months ago. On Earth, sunrise at the south pole means that southern spring has arrived. We don't often think of asteroids as having seasons, but they do: Like Earth, Eros passes through two solstices (when the Sun shines down over the poles) and two equinoxes (when day and night are of equal length) during its 1.76 year circuit around the Sun. Seasons on Eros last different lengths of time (northern spring is only half as long as autumn) while the apparent size of the Sun nearly doubles between fall and spring. The difference in polar surface temperatures from summer to winter may be as great as the difference between liquid nitrogen and boiling water - the seasons on Eros are truly alien. |
| ||||||||
Better predictions for the arrival of Coronal Mass Ejections at the Earthshould become possible with a new model. The problem is that these CMEs leave the Sun at different speeds, sometimes slower, in other cases faster than the solar wind - any speed between 20 and 2000 kilometers per second is possible. Slower CMEs will be accelerated while faster ones could be slowed down while travelling between the Sun and the Earth, an effect that the new model has incorporated. A key problem remains: The initial speed cannot be measured very accurately because the CME is moving directly towards the Earth and can only be seen (in SOHO LASCO images) as an expanding cloud, a 'halo event'. Only future spacecraft looking at the Sun 'from the side' will improve the situation.The formula used in the new model is remarkably simple: The acceleration is assumed to be proportional to the initial speed of CMEs, as in Acceleration [meters per second per second] = 1.41 - 0.0035 x CME speed [kilometers per second]. A possibility to test the model, which had been validated with many historical satellite data, came this June 6th: SOHO/LASCO and EIT had observed a full halo CME at 15:54 UT, surrounding the occulting disk. The plane-of-sky speed of the leading edge of the halo was measured to be about 908 km/s near the Sun. This was an ideal event for testing the model, because the CME originated close to the disk center and headed towards Earth. The model predicted a travel time of 2 1/2 days, so the CME was expected to arrive around 4 UT on June 09. The CME arrived at 22 UT on June 08, about 6 hours earlier than the prediction but within the claimed accuracy of 12 hours. (A major interplanetary shock driven by that CME hit the Earth half a day earlier by the way - that's normal.) |
|
NASA's recent failures were predictable - mathematicallyThe first detailled analysis of when a 'cheap' NASA mission succeeds and when it fails has turned up an almost inevitable law: If, for a given complexity of the mission there is either too little time or too little money, it will almost certainly fail. (AW&ST of June 12, p. 47-49, also available online)Goldin accepts blame for failures in Congress hearing but doesn't ask for more money: Fla. Today, SpaceViews, Space.com. House passes NASA budget, making few changes: SpaceViews. Problem aborts space shuttle main engine test firingA space shuttle main engine equipped with a next-generation fuel turbopump was damaged during an aborted test firing last week: Spaceflight Now, NASA statement, SpaceViews, Fla. Today.SeaLaunch declared ready for next mission in about one month: Space.com Futuristic spy satellite snaps clear picturesMTI, a small U.S. spacecraft launched in March to test advanced imaging technologies for possible use by next-generation spy satellites (see Update # 181 story 5), has gone to work: Spaceflight Now, Discovery.New Terra pictures from MISR: 2609, 2610. Eight new SRTM images have been published in recent weeks: # PIA0275... 2, 3, 4, 5 (nice anaglyph!), 6, 7, 8, 9 (particularly impressive!). Russian space pictures for sale with high resolution: NYT. Meteorite trouble at Hayden Planetarium solvedThe heads of New York City's Museum of Natural History and an American Indian group signed an agreement on June 22 to share custody of a 10,000-year-old meteorite that's a centerpiece of the museum's new planetarium: Details of the agreement, AP, NYT, Space.com. |
900 asteroids > 1 km in the inner solar systemA new study portrays the paths of asteroids in the inner solar system as a vast traffic system crisscrossed with superhighways along which are hurtling huge, rocky projectiles - the study estimates that an armada of asteroids, 900 strong, all a kilometer in diameter or larger, present a potential hazard to life on Earth: Cornell Press Release, Space.com, Discovery, SpaceViews, SPIEGEL, ENN.First Mir tourist to fly in early 2001Before then-60 year old Dennis Tito can go on an about week-long ride to Mir, another Russian crew has to go up and bring the space station out of hibernation - Tito's flight will thus not take place until about April, 2001. The launch dates for the next Mir flights are to be announced in mid-July: MirCorp Press Release, SpaceViews, BBC, CNN, Fla. Today ( earlier), Gannett, AP, SpaceRef, Wired, Discovery, NYT.Zvezda called ready: Fla. Today. Space station funding survives in House: Fla. Today. ESA, Canada renew cooperation once again: CSA, ESA Press Releases, SpaceViews.
|
All other historical issues can be found in the Archive.
The U.S. site of this Cosmic Mirror has been visited
since it was issued (the German site has no counter).
Compiled and written by Daniel Fischer
(send me a mail to [email protected]!), Skyweek
