Asteroidi,komete,meteori

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Smashing success for Deep Impact probe

In a triumph of cosmic marksmanship, a NASA probe has smashed into Tempel 1, releasing a spray of ancient debris from the comet's core.

The spacecraft Deep Impact released a copper-reinforced probe, which was the size of a washing machine and weighed a third of a tonne, on 3 July. The probe was travelling at 37,000 kilometres per hour when it smashed into the comet at about 05:52 GMT on 4 July. Deep Impact watched the crash from a safe distance.

"The impactor has been totally vaporized," says Rick Grammier, mission manager at the Jet Propulsion Laboratory in Pasadena, California. "We were right on target."

Scientists hope that the shape of the crater will reveal the strength of the comet's crust, and that the debris thrown outwards will hold clues about the characteristics of the early Solar System.

Comets are dirty snowballs, left over from the formation of the planets some 4.6 billion years ago. They probably delivered water and simple carbon molecules to the primitive Earth, shaping the chemistry that ultimately led to life on our planet. But very little is known about their internal composition and structure.

Analysing pristine material from inside Temple 1 will be like stepping back in time, says Andrew Coates of the Mullard Space Science Laboratory at University College London, who watched the first images arrive at a press briefing in London. "It's one of the most audacious experiments ever attempted," he says.

Bigger blast



Read Mark Peplow's diary blog entry from the Deep Impact press briefing.
Deep Impact watched the show for about 13 minutes before battening down its hatches to avoid flying debris. The craft is sending its analysis of the chemical composition of the plume back to Earth during the following 24 hours. But the shape and brightness of the cone of ejected material is already giving scientists clues about the structure of the Tempel 1 core, which is about 4 kilometres wide and 14 kilometres long.

"A large amount of material has been ejected; far more than people anticipated," says Paul Roche, an astronomer from University of Wales, Cardiff. Roche works on the Faulkes Telescope in Hawaii, which captured images of the collision. The large plume suggests that the comet's crust is weaker than expected, explains Coates, and this improves our chances of seeing material that has lain inside Tempel 1 since it first formed.

"Presumably we have a very large crater," agrees Michael A'Hearn, the mission's principle investigator from the University of Maryland, College Park. A'Hearn estimates that the hole could be the size of a football stadium.

More information is flooding in from observatories around the world and in space, in what some are calling the largest astronomical effort in history.

Tiny nudge

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The US$330-million Deep Impact mission was launched on 12 January 2005. Once it had the comet in its sights, the impactor probe used a self-targeting mechanism to aim at the brightest spot on the comet, now roughly 134 million kilometres away from Earth. Its camera recorded the fatal dive until just three seconds before impact. From up close, the camera recorded the craters left by previous meteorite collisions.

The impact delivered the same force as about 5 tonnes of TNT, says Roche. But there were never any fears that the comet would be destroyed or pushed towards the Earth, he adds. The impact has nudged the comet so slightly that in 20 years' time it will have strayed only 300 metres from its normal path.

Previous space missions have investigated the surfaces of comets Halley, Borrelly and Wild 2, and the European Space Agency's probe Rosetta hopes to drop a lander on the surface of comet Churyumov-Gerasimenko in May 2014.

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Dopuna: 28 Jul 2005 10:53

Sta je sledece sa Deep Impact

LOS ANGELES, California (AP) -- NASA is considering an encore for its Deep Impact spacecraft, which made history earlier this month when it smashed a hole in a comet to study its frozen primordial core.

While the space agency has not approved a specific future mission, it gave scientists at its Jet Propulsion Laboratory in Pasadena the go-ahead to bring the spacecraft closer to Earth's orbit for a potential mission extension.

"We're trying to maintain as many options as we can," Andrew Dantzler, the director of NASA's solar system division, said Tuesday.

Deep Impact planned to fire its thrusters Wednesday to slightly change course in a maneuver that will bring it back to Earth by 2008.

The spacecraft then will switch to safe mode to conserve energy until it receives orders for a possible second mission. If left untouched, the spacecraft will drift farther away.

The original mission called for the mothership to release an 820-pound copper impactor into the path of the onrushing comet Tempel 1, record the collision from a distance and retire as space junk.

But the mothership remained surprisingly healthy despite being bombarded with debris during a close flyby of Tempel 1 minutes after the collision.

Members of the Deep Impact team hope the maneuver will allow the spacecraft to steer toward 85P/Boethin, a comet that was discovered in 1975 and orbits the sun every 11 years.

Since Deep Impact carried only one impactor, any future mission will not cause a cosmic smashup. Instead, scientists hope the scientific instruments aboard Deep Impact will allow them a detailed glimpse of yet another comet.

Mission principal investigator Michael A'Hearn said a possible extended project would cost about $32 million; the Deep Impact mission cost $333 million.

The July 4 collision 83 million miles from Earth gave off two flashes of bright light and carved a crater in the potato-shaped comet. A larger-than-expected debris cloud extended thousands of miles into space, and has prevented scientists from peering into the comet's interior.

The impactor vaporized as it crashed on the comet's sunlit side, but the mothership survived unharmed. It flew within 310 miles of Tempel 1 and took pictures of the comet as it flew away.

Comets are irregular bodies of ice and dust that orbit the sun and were born about 4.5 billion years ago -- nearly the same time as the solar system itself. When a cloud of gas and dust condensed to form the sun and planets, comets formed from what was left over. Studying them could shed light on how the solar system formed.

Deep Impact blasted off in January from Florida for a 268-million-mile journey toward Tempel 1, which was discovered in 1867 and moves around the sun in an elliptical orbit between Mars and Jupiter every six or so years.

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Ovde se kace sve teme vezane za komete,asteroide,meteore

Eros


Scientists have stumbled on a way to passively monitor the shaking of an asteroid to learn what it is made of.



A new study of four-year-old data from NASA's NEAR-Shoemaker mission indicates that a set of vibrations caused by a collision with another space rock played a major role in sculpting the surface of asteroid Eros.

The idea was first put forth in 2001, but it was speculative. Now, an outside expert says, they hypothesis is solid as a rock, and it tells a story of Eros' composition.

Importantly, similar analyses could be used to passively peek inside other space rocks.

Eros is 20 miles (33 kilometers) long and about 8 miles (13 kilometers) wide. It is the most well studied asteroid. NEAR-Shoemaker mapped Eros in detail back in 2000-2001 before officials executed a controlled and dramatic crash landing, the first-ever touchdown on an asteroid.

Like any asteroid, Eros has been banging around the solar system in some form for about 4.5 billion years.

In the early days of the solar system, when things were more crowded, collisions were frequent. Some large asteroids become smaller. Some small rocks stuck together and grew. Many were scooped up by the fledgling Earth and the other planets.

The asteroids that remain, confined mostly to a belt between Mars and Jupiter, harbor a tale of the solar system's formation. But first scientists have to figure out how to read their language, with an alphabet of craters and razbijacs and a grammar based largely on mineral composition and density.

Among Eros' most striking features is an impact crater 4.7 miles (7.6 kilometers) wide that scientists have determined was carved fairly recently. Another curious aspect to Eros is that across nearly 40 percent of its surface, all craters up to about a third of a mile (0.5 kilometers) wide have been erased.

The smooth surface has puzzled scientists since the NEAR landing.

The new study, led by Cornell University researcher Peter Thomas, nixed one theory by determining that the vanished craters could not have been covered by material ejected in the recent large impact. Further, the locations of the erased craters suggests they were jiggled out of existence by the internal vibrations caused in the impact.

The hypothesis, if right, can be used to glean an idea of how the asteroid is constructed. Scientists have long wondered if asteroids were solid rocks or, as is likely in at least some cases, loose piles of rubble that have undergone many collisions and managed to hang together.

"Our observations indicate that the interior of Eros is sufficiently cohesive to transmit seismic energy over many kilometers, and the outer several tens of meters [yards] of the asteroid must be composed of relatively non-cohesive material," Thomas and his colleague, Mark Robinson of Northwestern University, write in the July 21 issue of the journal Nature.

That outer non-cohesive stuff would be regolith, which on Earth is called dirt and on our nearest natural satellite is known as Moon dust.

"For the first time, the authors provide convincing evidence that makes this conclusion more than just reasonable conjecture," says Erik Asphaug, a scientist at the University of California, Santa Cruz who was not involved in the study.

The results confirm what Thomas first suspected back in 2001 and what University of Arizona's James Richardson Jr. found in separate work last year.

The findings are likely to remake the way asteroids are studied.

Scientists have used craters as a way to figure out how ancient or fresh a space rock's surface is. Myriad small craters suggest a long history and thus an old surface. A smoother surface with fewer craters would imply a rock had recently been cleaved or somehow resurfaced.

At least that was the thinking.

"This asteroidal Botox calls into question the habit of dating asteroid surfaces through their cratering record," Asphaug writes in a separate analysis in the journal.

A rubble pile, Asphaug explains, would dampen vibrations during an impact. That would leave more small craters intact, causing the asteroid to appear older based on the conventional method of analysis.

Eros, while it has a deep surface of loose material, is solid enough on the inside, at least in parts, to transmit seismic waves efficiently.

If convention is indeed overturned, the shift could be a boon to space rock studies.

The finding suggests large and newer impact craters, like the one on Eros, could be used as proxies for seismic data, Asphaug points out. The insides of other asteroids might be probed just by mapping their surfaces. "Thomas and Robinson's work also opens up a new way of looking at asteroids," he said.

Perhaps the passive technique could even go active.

Given the success of NASA's recent Deep Impact mission, which crashed a small probe into a comet, Asphaug sees value in a similar project that would first place seismic sensors on a space rock, so that the interior could be mapped during the collision.

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Asteroidi

Asteroids are material left over from the formation of the solar system. One theory suggests that they are the remains of a planet that was destroyed in a massive collision long ago. More likely, asteroids are material that never coalesced into a planet. In fact, if the estimated total mass of all the asteroids was gathered into a single object, the object would be less than 1,500 kilometers (932 miles) across - less than half the diameter of the Moon.
Thousands of asteroids have been identified from Earth. It is estimated that 100,000 are bright enough to eventually be photographed through Earth based telescopes.
Much of our understanding about asteroids comes from examining pieces of space debris that fall to the surface of Earth. Asteroids that are on a collision course with Earth are called meteoroids. When a meteoroid strikes our atmosphere at high velocity, friction causes this chunk of space matter to incinerate in a streak of light known as a meteor. If the meteoroid does not burn up completely, what's left strikes Earth's surface and is called a meteorite. One of the best places to look for meteorites is the ice cap of Antarctica.
Of all the meteorites examined, 92.8 percent are composed of silicate (stone), and 5.7 percent are composed of iron and nickel; the rest are a mixture of the three materials. Stony meteorites are the hardest to identify since they look very much like terrestrial rocks.
Since asteroids are material from the very early solar system, scientists are interested in their composition. Spacecraft that have flown through the asteroid belt have found that the belt is really quite empty and that asteroids are separated by very large distances.
The impact of a large asteroid can be truly catastrophic. For example some believe that the object that smashed into the Yukatan Peninsula 65 million years ago was the event that wiped out the dinosaurs. The Gulf of Mexico may mark the crater that it left behind. The asteroid that would have hit there would have been between 10-20 miles across. The hole in created was about 20 miles deep. It was converted instantly in white hot vapor as was its target and its surrounded areas.
A large asteroid hitting the earth would create debis that would crash down in neighboring areas. It would throw dust into the earth's atmosphere circling the globe, dimming the sunlight, ruining agriculture year round, probably ending civilization as we know it.
At this point in time NORAD has a limited number of people monitoring the skies for asteroids. An asteroid would come in quickly. Asteroids must be tracked.
Space Guard is an international network of telescopes where people work together to track asteroids and divert them from hitting the earth. Blowing up an asteroid is not the answer as large pieces still would impact on the earth and do lots of damage anyway.
The Earth is continually encountering interplanetary debris of various sizes. Although the rarity increases with size, we know there are asteroids big enough to cause a catastrophe if they collided with the Earth. Because of the perturbing influence of the major planets, the asteroid orbits tend to "wander", and the calculation of whether (or when) a particular object might impact the Earth may require extremely accurate knowledge of the orbit, such as can be provided by radar observations.
The solar system has a large number of rocky and metallic objects that are in orbit around the Sun but are too small to be considered full-fledged planets. These objects are known as asteroids or minor planets. Most, but not all, are found in a band or belt between the orbits of Mars and Jupiter. Some have orbits that cross Earth's path, and there is evidence that Earth has been hit by asteroids in the past. One of the least eroded, best preserved examples is the Barringer Meteor Crater near Winslow, Arizona.


ASTEROID GASPRA #951


ASTEROID IDA #246

Ida, like Gaspra, is an S-type asteroid, meaning that it is a reddish object composed of a mixture of the minerals pyroxene, olivine, and iron. Approximately one-sixth of all known asteroids fall within the S-type category. Gaspra and Ida like other S-class asteroids are the parent bodies of some types of basaltic meteorites. The Galileo sent back pictures of main-belt asteroids (Gaspra and Ida) during the mission's cruise to Jupiter.

Pojas asteroida


A countless number of asteroids are distributed around the sun. The doughnut shaped concentration of these found between the orbits of Mars and Jupiter is referred to as the asteroid belt.
Asteroid belt estimated to contain over 1 million asteroids with diameter exceeding one kilometer.


The Ceres Asteroid is the largest in the asteroid belt. Asteroids contained within this belt generally orbit the Sun in a stable and essentially circular trajectory. However, a portion of asteroids subject to the gravity of Jupiter undergo a changer in orbit toward the center of the solar system. Asteroids which in this manner draw close to the Earth's orbit are referred to as near Earth objects (NEO), and are considered to pose the danger of potential impact with Earth.



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Komete



Комете ( грч. kometes- дугокос) се састоје од камења, прашине и гасова, а на њима се могу издвојити два дијела: лоптаста глава или језгро и реп. Језгро комете је величине од 1-2 km и састоји се од леда, прашине и камења. Након што Сунчеви зраци загрију језгро комете, гасови се рашире у облику косе (коме), која заједно са језгром чини главу комете, која достиже и до 100 000 km. Приближавањем Сунцу развија се и реп, чија дужина може бити и до више стотина милиона колометара. Репови комета су дугачки и магличасти, грађени од веома разријеђене прашине и плазме. Још их називају и звијезде репатице. Због веома мале густине за комете се каже да су „огромно видљиво ништа“. У циљу објашњавања густине комета један руски научник је рекао: „Узмите зрно пшенице и одвојите од њега милионити дио. Тај дјелић истуцајте у нејфинију прашину, а затим је разбацајте по некој великој дворани у којој има више од 1000 сједишта. Да ли та количина прашине нешто значи у толикој сали? Ето, толика је управо густина материје у репу комете.“

Комете су видљиве када дођу у близину Сунца и Мјесеца, а њихово појављивање у прошлости људи су тумачили као предзнаке ратова и епидемија. Дијеле се на три основне групе: елиптичне,параболичне и хиперболичне. Комете се састоје од воденог леда, нешто угљеног диоксида, метана и амонијака, те од прашине и стјеновитих честица. Могу се подијелити на кратко-периодичне (до 200 година) и дуго-периодичне (преко 200 г.). Кратко периодичнe се крећу око Сунца истим смјером као и планете, док дуго-периодични могу доћи из било ког смјера. Извор дуго-периодичних комета је Оoртов облак којег чини сферни облак кометских језгри које чине крајњу границу Сунчевог система. Велики број комета као и астероида налазе се у Куиперовом појасу који се налази иза Нептуна. Разлог зашто објекти из Куиперовог појаса никад нису постали небеска тијела је тај што имају мању густину праоблака на великој удаљености од Сунца.

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Халејева комета

Најпознатија комета је Халејева комета која се појављује у Сунчевом систему сваких 76 година (последњи пут је прошла поред Сунца фебруара 1986. године).До тог закључка дошао је енглески научник Едмонд Халеј у 18.вијеку по коме она и носи име. Сматра се да је ова комета већ 40 пута обилазила око Сунца. Током последњег повратка Халејеве комете извршен је велики научно-истраживачки програм проучавања самог језгра. Двије руске сонде, Вега 1 и Вега 2 прошле су поред језгра комета на око 8000 км и послале су око 1200 фотографија. Европска летилица Гиото прошла је 14. марта 1986.год. на само 540 км од језгра.Тада је утврђено да је језгро црне боје са неколико активних испусних отвора из којих је избацивана велика количина прашине. Само језгро комете је неправилног облика, величине 15 х 8 км.Никада раније није било снимљено језгро комете, а Халејева комета је дала многе одговоре на питања везана уз ова небеска тијела.

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Meteori



Метеори ( грч. meteoros- лебдећи, висећи) су тамна, мала и хладна небеска тијела која настају распадањем комета и других небеских тијела (астеорида, а постоје и докази да неки метеорити, пронађени на Земљи потичу са Марса). Крећу се појединачно или у ројевима без сталне путање и могу бити различитих величина (од зрнаца прашине до неколико десетина метара). Са Земље видимо метеоре у току ведрих ноћи као звијезде које падају са неба па се нагло угасе или као варнице које прелијећу преко неба.То се дешава када метеори великом брзином улете у Земљину атмосферу, гдје се усијају и испаре усљед трења са ваздухом.

Метеори ( грч. meteoros- лебдећи, висећи) су тамна, мала и хладна небеска тијела која настају распадањем комета и других небеских тијела (астеорида, а постоје и докази да неки метеорити, пронађени на Земљи потичу са Марса). Крећу се појединачно или у ројевима без сталне путање и могу бити различитих величина (од зрнаца прашине до неколико десетина метара). Са Земље видимо метеоре у току ведрих ноћи као звијезде које падају са неба па се нагло угасе или као варнице које прелијећу преко неба.То се дешава када метеори великом брзином улете у Земљину атмосферу, гдје се усијају и испаре усљед трења са ваздухом. Пролазак дијелова космичке материје кроз Земљину атмосферу изазива појаву свјетлог трага који се зове метеор (грч. meteoron-ваздушна појава). Веома мала и невидљива тијела која круже око Сунца у безваздушном простору, називају се метеориди. Када Земља пресјече путању метеорида, он улази у Земљину атмосферу, сагорјева и емитује свјетлост. Та појава се назива метеор. Ако тијело метеорида не сагори у потпуности у атмосфери, оно пада на Земљу остављајући траг у виду кратера.Тијело које падне на површину Земље назива се метеорит. Охлађени метеорити изгледају као „сунђери од зарђалог гвожђа“. Сматра се да на Земљу дневно падну милиони метеорита укупне масе око 15 000kg, који изгледају као киша небеске прашине и камења, појединачне масе мање од 1mg. Метеори се могу подијелити по припадности одређеном метеорском потоку или роју. Метеорски поток је скуп елиптичних метеорида који круже око Сунца, док је метеорски рој скуп згуснутијих метеорских тијела који такође круже око Сунца.

Када Земља пресјече одређени поток или рој чини се као да сви метеори долазе из једне тачке на небу, која се назива радијант (лат. radiare-зрачити). Потоци и ројеви добијају називе у зависности од тога у ком се сазвјежђу или близу које звијезде се њихови радијанти налазе (нпр.Персеиди, Леониди,Геминиди, ета-Аквариди, гама-Дракониди..) Иначе,Геминидима треба око 1.5 до 1.65 година да обиђу Сунце (претпоставља се да они потичу од комете која је прије 15 000 год. посјетила Сунчев систем.)

Метеори који не припадају ни једном потоку или роју зову се спорадици, а веома сјајни метеори који парају небо уз јаку буку зову се болиди.

Брзине метеора крећу се у просјеку од 11km/s до 72km/s. Видљиви траг метеора настаје на 130km од површине Земље, а престаје на око 70km.

Комете приликом проласка кроз Сунчев систем оставе дио свог материјала који се под утицајем гравитације околних небеских тијела групише у меторске потоке или ројеве. Веома ријетка појава дешава се када се комета потпуно распадне и формиора поток који садржи пуно метеорског материјала. Том приликом након проласка Земље поред дотичног потока, може се видјети како метеор сваке секунде запара небо.

Најпознатији су Леониди,крхотине кометеTempel-Tuttl.Пљусак Леонида догађа се сваке године од 14. до 20 .новембра, са максумумом око 17 новембра.

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Dopuna: 07 Avg 2005 0:36

ESA-ina misija Rosetta - prva letjelica koja će se spustiti na komet

Misija Europske svemirske agencije (ESA-e) pod nazivom Rosetta, bit će prva misija kojoj je cilj spustiti se na komet. Ova je misija vrlo važna jer će nam dati uvid u strukturu i svojstva kometa o kojima ne znamo mnogo

Rosetta will be the first mission ever to land on a comet. After its lander reaches the comet, the main spacecraft will follow the comet for many months as it heads towards the Sun. Rosetta's task is to study comets, which are considered the primitive building blocks of the Solar System. This will help us to understand if life on Earth began with the help of 'comet seeding'.

Rosetta is one of the most challenging missions ever attempted. Many of the complex navigation and landing manoeuvres need to take place automatically with absolutely no room for error. The complications of sending a small spacecraft halfway across the Solar System and making a soft landing on a small comet are immense.

A large number of complex scientific instruments need to be accommodated on one side of the spacecraft, which must permanently face the comet during the operational phase of the mission.
The spacecraft needs to endure both extremes of temperature, from that of deep space to very close to the active comet
Complex spacecraft navigation needs to take place at low-altitude orbits around the dust and gas jets of the comet, which also has a weak but asymmetrical rotating gravity field.
The Rosetta lander has to be stowed to survive the cruise and eventually to self-eject from the spacecraft. The orbiter must navigate with millimetre accuracy for the ejection, and then relay data from the lander back to Earth.



What's special?
Rosetta will be the first space mission to journey beyond the main asteroid belt and rely solely on solar cells for power generation, rather than the traditional radio-isotope thermal generators. The new solar-cell technology used on the orbiter's two giant solar panels allows it to operate over 800 million kilometres from the Sun, where sunlight levels are only 4% of those on Earth. Hundreds of thousands of specially developed non-reflective silicon cells generate up to 8700 Watts in the inner Solar System and around 400 Watts for the deep-space comet encounter
The Rosetta mission will achieve many historic firsts:

Rosetta will be the first spacecraft to orbit a comet's nucleus.
It will be the first spacecraft to fly alongside a comet as it heads towards the inner Solar System.
Rosetta will be the first spacecraft to examine from close proximity how a frozen comet is transformed by the warmth of the Sun.
Shortly after its arrival at the comet, the Rosetta lander will make the first controlled touchdown on a comet nucleus.



Spacecraft
The main spacecraft measures 2.8 x 2.1 x 2.0 metres, on which all subsystems and payload equipment are mounted. There are two 14-metre solar panels with a total area of 64 square metres. At launch, the vehicle weighs approximately 3000 kilograms (fully fuelled) including 1670 kilograms of propellant, 165 kilograms of scientific payload for the orbiter, and 100 kilograms for the lander.
The large number of complex scientific instruments needs to be accommodated on one side of the spacecraft, which must permanently face the comet during the operational phase of the mission. Until its release, the lander is carried on the opposite side of the orbiter to the large high-gain antenna dish.

As it arrives on the comet, the Rosetta lander uses three different techniques (self-adjusting landing gear, harpoons, and a drill) to ensure that once it has arrived on the surface of the comet, it stays there.

As soon as it touches down, two harpoons will anchor the probe to the surface, the self-adjusting landing gear will ensure that it stays upright, even on a slope and then the lander's feet will drill into the ground. These devices will help counteract the fact that there is very low gravity on a comet. The lander will focus on the study of the composition and structure of the comet nucleus material. Goals include the determination of the elements that exist, traces of minerals and isotopic composition of the comet's surface and immediate subsurface. The comet's surface strength, density, texture, porosity, ice phases and thermal properties will also be studied. Texture investigations will include microscopic studies of individual grains.


Journey
The journey to Rosetta's final destination will involve complex fly-bys of other planets.


Partnerships
The orbiter's scientific payload includes 11 experiments and the small lander which is equipped with its own payload of scientific instruments. Scientific consortia from institutes across Europe and the United States have provided these state-of-the-art instruments.

The lander is provided by a European consortium headed by the German Aerospace Research Institute (DLR). Other members of the consortium are ESA, CNES and institutes from Austria, Finland, France, Hungary, Ireland, Italy, and the United Kingdom.

Pogledaj

Dopuna: 08 Avg 2005 23:22

Udar meteora,je start novog zivota
Meteor impacts are generally regarded as monstrous killers and one of the causes of mass extinctions throughout the history of life. But there is a chance the heavy bombardment of Earth by meteors during the planet's youth actually spurred early life on our planet, say Canadian geologists.

A study of the Haughton Impact Crater on Devon Island, in the Canadian Arctic, has revealed some very life-friendly features at ground zero. These include hydrothermal systems, blasted rocks that are easier for microbes to inhabit, plus the cozy, protected basin created by the crater itself. If true, impact craters could represent some of the best sites to look for signs of past or present life on Mars and other planets.

A presentation on the biological effects of impacts is scheduled for Monday, 8 August, at Earth System Processes 2, a meeting co-convened by the Geological Society of America and Geological Association of Canada this week in Calgary, Alberta, Canada.

The idea that meteor impacts could benefit or even create conditions suitable for the beginning of early life struck Canadian Space Agency geologist Gordon Osinski while he and colleagues were conducting a geological survey of the 24-kilometer (15-mile) diameter Haughton Crater. Along the rim of the crater they noticed what looked like fossilized hydrothermal pipes, a few meters in diameter.

"That set the bells ringing about possible biological implications," said Osinski. Hydrothermal systems are thought by many people to be the favourable places for life to evolve."

Detailed mineralogical analyses have since revealed that when the Haughton meteor smacked into the icy ground 23 million years ago it created not only a crater, but fractured the ground in such a way as to create a system of steamy hydrothermal springs reaching temperatures of 250 degrees C. The heat appears to have gradually dropped over a period of tens of thousands of years, the researchers report.

Besides providing heat and razbijacing the ground, the impact also created pore spaces in otherwise dense granitic rocks, giving microbes more access to the minerals and the surfaces inside the rocks - basically more real estate and more supplies.

The shocked rocks are also more translucent, which would be beneficial to organisms that possessing with any photosynthetic capabilities.

A crater shape itself also might serve as a protective environment, says Osinski. As such, impact craters are also good places to store evidence of past life. On Earth many craters fill with water and become lakes. Lakes accumulate sediments, the layers of which are a geological archive of the time after the crater formed. The Haughton Impact crater, for instance, contains the only Miocene-age sediments in the entire Canadian Arctic.

"One of the most interesting aspects of the Haughton Impact Crater is that it's in a polar desert," said Osinski. The dry, frigid weather makes for a barren landscape that's easy to study, he said. The same features make it one of the more Mars-like places on Earth.

"Most people put impacts with mass extinctions," said Osinski. "What we're trying to say is that following the impact, the impact sites are actually more favorable to life than the surrounding terrain."

It's interesting to note, says Osinski, that on Earth the heaviest meteor bombardment of the planet happened at about the same time as life is believed to have started: around 3.8 billion years ago. Impact craters of that age were long ago erased on Earth by erosion, volcanic resurfacing and plate tectonics.

But other planets and moons - including Mars - still bear the cosmic scars of that early debris-clogged period in the solar system. It may be possible, therefore, that the best places to look for at least fossil evidence of life on Mars is inside those very same craters, he said.

"What we're doing is trying to narrow down the search area," said Osinski.

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Deep Impact pokazao da je kometa bogata ugljenicima!

'Impact' Comet Is Rich in Carbon
Collision Suggests Porous Structure

By Guy Gugliotta
Washington Post Staff Writer
Wednesday, September 7, 2005; Page A04

When NASA's Deep Impact projectile hit Comet Tempel 1, it produced a giant plume of gas and dust far richer than expected in carbon compounds, reinforcing the view that comets may have contributed the chemical raw materials that produced life on Earth.

Scientists said Tuesday they do not know how typical Tempel 1 is, but they expect eventually to put together the first-ever complete profile of the substances that comets may have brought to Earth 4.5 million years ago.


Scientists at the NASA Jet Propulsion Laboratory in Pasadena, Calif., observe the impact of a projectile with the Comet Tempel 1. The resulting plume revealed a comet that has a porous structure but otherwise contains carbon compounds common on Earth. (Pool Photo By Robert Lachman)

"This will be the biggest contribution we will make," said University of Maryland astronomer Michael A'Hearn, lead scientist for NASA's Deep Impact mission. "Many hydrocarbons are in higher abundance than one would expect, and there are many others we haven't identified yet."

A'Hearn spoke during a telephone news conference to announce the first research findings from the spectacular July 4 rendezvous in space between Tempel 1 and the 820-pound copper-tipped "impactor" that slammed into it just before 2 a.m. Eastern time on Independence Day. The findings are to be published Thursday in the journal Science.

A'Hearn said data transmitted from the "flyby" spacecraft that accompanied the impactor offered several mildly surprising results, but "nothing that knocked my socks off." The flyby spacecraft dropped the impactor into the path of the comet, then photographed the encounter from a safe distance.

Horst Uwe Keller of Germany's Max Planck Institute said the impact threw about 5,500 tons of water into space, along with other types of ice -- including carbon dioxide, carbon monoxide and ammonia ice. But the impact tossed up an even greater quantity of dust.

A'Hearn said analysis of the dust had found hydrogen cyanide, methyl cyanide, acetylene and formaldehyde, with many other organic compounds still to be identified, adding that the presence of such compounds in such large quantities suggested a closer relationship between comets and the origins of life on Earth, Ahearn said.

Keller, who supervised observations of the impact from the European Space Agency's Rosetta spacecraft about 50 million miles away, said the "density of the comet is very low and the porosity is very high," and described the texture as "crumbly."

A'Hearn said the impactor hit the comet at an oblique angle and plowed into it to a depth of "tens of meters," but could not be more specific because the plume of powdery ice and dust that spouted upward was so thick that scientists have not finished electronically manipulating the images to be able to view the crater.

A'Hearn said he had expected the plunging impactor eventually to "reach a layer" where the comet was denser, but that did not happen: "I'm not convinced there is a solid layer," A'Hearn said. "We think something like 75 to 80 percent" of the comet "is empty space."

Another as-yet-unexplained phenomenon was the apparent presence of craters on the surface of Tempel 1, as if the comet had been struck by meteors or other space rocks during its journeys. Neither of two other comets previously photographed by spacecraft show such craters, which A'Hearn said mimicked a typical impact pattern like that found on the moon.

Comets, composed principally of dust and ice, wander periodically into the inner solar system from deep space, and some scientists have suggested that they may have brought water and organic compounds to the early Earth. A'Hearn said nothing he had found out about Tempel 1 so far had led him to disagree with the usual characterization of comets as "dirty snowballs."

But though comets display a showy "tail" as they approach the sun, their cores are composed of icy material essentially undisturbed by earthquakes, volcanoes or erosion since the solar system's formation 4.5 million years ago.

Deep Impact was designed to punch through Tempel 1's surface to get a first-ever look at a comet's primordial core and begin analyzing what influence comets may have had on the Earth's evolution. Besides the fly-by spacecraft and Rosetta, about 80 Earth-based telescopes observed the collision and gathered data.

Ovde

Dopuna: 09 Sep 2005 10:05

Komete nemaju cvrsto jezgro?
Comets May Not Have Solid Cores, "Impact" Shows
Brian Handwerk
for National Geographic News

September 8, 2005

NASA scientists didn't know quite what to expect when they crashed a half-ton spacecraft into the approximately four-mile-wide (six-kilometer-wide) Comet Tempel 1 on July 4.

Now initial findings from the groundbreaking experiment are challenging current theories about comets and their creation. The results could even impact theories of planetary construction and the birth of life on Earth.

One surprising revelation from the 23,000-mile-an-hour (37,000-kilometer-an-hour) collision is that Tempel 1 is a fragile ball composed of powdery fragments of ice and dust.

"We looked inside [a comet] for the first time," said Michael A'Hearn, an astronomy professor at the University of Maryland in College Park and the lead investigator for the Deep Impact mission.

"We learned that the outer several tens of meters of cometary material is unbelievably fragile, less strong than a snowbank," A'Hearn said. "It's mostly porous, mostly empty. There's no indication yet of reaching a solid layer, so if there is one, it must be down some tens of meters."

Infrared images reveal that Tempel 1's surface warms and cools quickly with changing amounts of sunlight. This rapid change suggests a porous, rather than solid, surface.

But Tempel 1's fragility is more than skindeep. Observational data also suggest that the overall density of the comet is quite low.

"I'm not convinced that there is a solid layer under there," A'Hearn said. "If you look at the icy dust and the density we've deduced for the nucleus itself, something like 75 or 80 percent of the nucleus is empty space. So that tells me that there may be no solid layer."

A'Hearn and others reported results of the Deep Impact mission in today's issue of Science Express, the online advance version of the research journal Science.

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Japanska sonda
The Japanese Hayabusa spacecraft has approached within 20km (12 miles) of the asteroid it has been travelling to for more than two years.

The probe will collect a sample from the surface of asteroid Itokawa and return it to Earth for analysis.

Mission scientists hope this will shed light on how these mysterious Solar System bodies formed and evolved.

Hayabusa has been using an efficient ion engine propulsion system to reach its target.

The probe will now hover where it is, gathering data on Itokawa from a distance.

Sample return

The plan is for the probe to land on the asteroid, collect a sample from the surface and return it to Earth. Hayabusa's sample-return canister should parachute back to Earth in the summer of 2007.

A new image taken by the spacecraft's camera on 12 September shows the contrast between hilly regions and a smooth area on the asteroid.
Vise

Dopuna: 14 Okt 2005 0:17

U kometama vise prasine nego leda
Observations of Comet 9P/Tempel 1 made by ESA’s Rosetta spacecraft after the Deep Impact collision suggest that comets are ‘icy dirtballs’, rather than ‘dirty snowballs’ as previously believed.

Comets spend most of their lifetime in a low-temperature environment far from the Sun. Their relatively unchanged composition carries important information about the origin of the Solar System.

On 4 July this year, the NASA Deep Impact mission sent an ‘impactor’ probe to hit the surface of Comet 9P/Tempel 1 to investigate the interior of a cometary nucleus.

The 370 kg copper impactor hit Comet Tempel 1 with a relative velocity of 10.2 kilometres per second. The collision was expected to generate a crater with a predicted diameter of about 100-125 metres and eject cometary material. It vaporised 4500 tonnes of water, but surprisingly released even more dust.

Tempel 1's icy nucleus, roughly the size of central Paris, is dynamic and volatile. Possibly the impact would also trigger an outburst of dust and gas, and produce a new active area on the comet’s surface.

Just before impact, the Hubble Space Telescope spotted a new jet of dust streaming from the icy comet. No one knows for sure what causes these outbursts.

Rosetta, with its set of very sensitive instruments for cometary investigations, used its capabilities to observe Tempel 1 before, during and after the impact.

At a distance of about 80 million kilometres from the comet, Rosetta was in the most privileged position to observe the event.

European scientists using Rosetta's OSIRIS imaging system observed the comet’s nucleus before and after the impact. OSIRIS comprises a narrow-angle camera (NAC) and a wide-angle camera (WAC). Both cameras imaged the extended dust coma from the impact in different filters.

OSIRIS measured the water vapour content and the cross-section of the dust created by the impact. The scientists could then work out the corresponding dust/ice mass ratio, which is larger than one, suggesting that comets are composed more of dust held together by ice, rather than made of ice comtaminated with dust. Hence, they are now ‘icy dirtballs’ rather than ‘dirty snowballs’ as previously believed.

The scientists did not find evidence of enhanced outburst activity of Comet 9P/Tempel 1 in the days after the impact, suggesting that, in general, impacts of meteoroids are not the cause of cometary outbursts. Scientists also hope to make a 3D reconstruction of the dust cloud around the comet by combining the OSIRIS images with those taken from ground observatories.
Ovde

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Napisano: 29 Jun 2021 22:24

Da li ste znali da kometa Hale Bopp koja je 97me godine krasila noćno nebo (ko se seća zna kolko je bila sjajna) možda ima mesec koji kruži oko jezgra komete?

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Dopuna: 29 Jun 2021 22:25

Vladimir ::The US Deep Impact spacecraft is on course to fire a probe into a comet on 4 July, scientists have announced.

The missile, travelling at 100 times the speed of a bullet, is expected to blast a hole in the heart of the space rock, spraying out ice and dust.

Analysing this primordial material, which was around at the time the Solar System formed, could shed light on the origin of the planets.

The collision is set for 0552 GMT on Independence Day in America.

About a day before, the mothership will release a small copper probe, which will steer itself towards Comet Tempel 1, a ball of ice, rock and dust the size of Manhattan.

Cameras on the projectile and the mothership will record the event, and instruments on Deep Impact will analyse the gases and debris ejected.

'Out of this world'

Rick Grammier, Deep Impact project manager at the US space agency Nasa's Jet Propulsion Laboratory in Pasadena, California, called the manoeuvre "extremely challenging".

"In our quest of a great scientific payoff, we are attempting something never done before at speeds and distances that are truly out of this world," he said.

Infographic

"It's a bullet trying to hit a second bullet with a third bullet, in the right place at the right time, watching the first two bullets and gathering the scientific data from that impact," he told a news briefing in Washington on Thursday.

Mission scientists said they expected to be able to solve a technical glitch that has caused the spacecraft to return blurry images from one of its instruments.

They will use a mathematical process on the images it captures after they have been transmitted to Earth.

Deep Impact has taken six months to travel some 431 million km (268 million miles) from Earth.

The mission shares a title with the 1998 Hollywood film in which astronauts attempt to stop a comet hitting the Earth.

Deep Impact aims to look under the surface of a comet, at material that has remained untouched since the birth of the planets.

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Evo i video na srpskom o toj čuvenoj sondi i njenim otkrićima

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Dopuna: 29 Jun 2021 22:27

Evo i zanimljivost o čuvenoj Halejevoj kometi. Da li ste znali da je čak 5 sondi posetilo ovu kometu tokom proleta 1986 godine?

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Dopuna: 23 Avg 2021 20:17

Zašto u pojasu asteroida nije formirana planeta? U ovom videu pokušavam da odgovorim baš na to pitanje!
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Dopuna: 17 Sep 2021 20:06

13-tog Septembra 2021 neki objekat je pogodio Jupiter i to je snimio astronom amater!
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Необичан астероид врти се све брже — нико не зна зашто

neobičan
menja boju, brzinu rotacije, nema leda....
ima rep i kišu meteora

Liči opis na svemirski brod iz Spilbergovog, Bliskog susreta treće vrste....

Citat:....треба имати у виду да се ротације астероида обично уопште не мењају.
Разумевање тога шта се догађа са Фајетоном могло би да пружи бољи увид у класу астероида који се сматрају „потенцијално опасним“, пошто понекад прођу близу Земље.

Има прашњав реп и један је од само два астероида који изазива кишу метеора.

На Фајетону, по свему судећи, за разлику од комете, нема леда, због чега га стручњаци називају „каменом кометом“. Упечатљиво је плаве боје, за разлику од већине астероида које су црвенкасте или сиве боје.

Светлост Фајетона се мења док се окреће око своје осе, а научници су успели да након неког времена одреде његов приближни ротацијски период од око 3,6 сати. Међутим, да би се на њега спустила летелица потребни су прецизнији подаци, због чега је научник Шон Маршал из Опсерваторије „Аресибо“ у Порторику почео да ради на детаљнијем одређивању његове величине, облика и ротације.

....Маршал је уочио нешто веома необично. Како је објаснио, Фајетонов период ротације пре посматрања 2021. постепено се мењао, могуће због његове активности када је био близу перихела у јануару 2020.

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