LCROSS Impact Data Indicates Water on Moon

回覆文章
dwond
主序星
文章: 140
註冊時間: 週二 13 11月, 2007 11:51

LCROSS Impact Data Indicates Water on Moon

文章 dwond » 週六 14 11月, 2009 04:40

LCROSS Impact Data Indicates Water on Moon
11.13.09

The argument that the moon is a dry, desolate place no longer holds water.

Secrets the moon has been holding, for perhaps billions of years, arenow being revealed to the delight of scientists and space enthusiastsalike.

NASA today opened a new chapter in our understanding of themoon. Preliminary data from the Lunar CRater Observation and SensingSatellite, or LCROSS, indicates that the mission successfully uncoveredwater during the Oct. 9, 2009 impacts into the permanently shadowedregion of Cabeus cater near the moon’s south pole.

The impact created by the LCROSS Centaur upper stage rocket created atwo-part plume of material from the bottom of the crater. The firstpart was a high angle plume of vapor and fine dust and the second alower angle ejecta curtain of heavier material. This material has notseen sunlight in billions of years.
圖檔
The visible camera image showing the ejecta plume at about 20 seconds after impact.
Credit: NASA

"We're unlocking the mysteries of our nearest neighbor and by extensionthe solar system. It turns out the moon harbors many secrets, andLCROSS has added a new layer to our understanding," said Michael Wargo,chief lunar scientist at NASA Headquarters in Washington.

Scientists have long speculated about the source of vast quantities ofhydrogen that have been observed at the lunar poles. The LCROSSfindings are shedding new light on the question of water, which couldbe more widespread and in greater quantity than previously suspected.

Permanently shadowed regions could hold a key to the history andevolution of the solar system, much as an ice core sample taken onEarth reveals ancient data. In addition, water, and other compoundsrepresent potential resources that could sustain future lunarexploration.
圖檔
Data from the down-lookingnear-infrared spectrometer. The red curve shows how the spectra wouldlook for a "grey" or "colorless" warm (230 C) dust cloud. The yellowareas indicate the water absorption bands.
Credit: NASA

Since the impacts, the LCROSS science team has been working almostnonstop analyzing the huge amount of data the spacecraft collected. Theteam concentrated on data from the satellite's spectrometers, whichprovide the most definitive information about the presence of water. Aspectrometer examines light emitted or absorbed by materials that helpsidentify their composition.

"We are ecstatic," said Anthony Colaprete, LCROSS project scientist andprincipal investigator at NASA's Ames Research Center in Moffett Field,Calif. "Multiple lines of evidence show water was present in both thehigh angle vapor plume and the ejecta curtain created by the LCROSSCentaur impact. The concentration and distribution of water and othersubstances requires further analysis, but it is safe to say Cabeusholds water."

The team took the known near infrared spectral signatures ofwater and other materials and compared them to the spectra collected bythe LCROSS near infrared spectrometer of the impact.

"We were only able to match the spectra from LCROSS data when weinserted the spectra for water," said Colaprete. "No other reasonablecombination of other compounds that we tried matched the observations.The possibility of contamination from the Centaur also was ruled out."
圖檔
Data from the ultraviolet/visible spectrometer taken shortly after impact showing emission lines (indicated by arrows). These emission lines are diagnostic of compounds in the vapor/debris cloud.
Credit: NASA
Additional confirmation came from an emission in theultraviolet spectrum that was attributed to hydroxyl, one product fromthe break-up of water by sunlight. When atoms and molecules areexcited, they release energy at specific wavelengths that are detectedby the spectrometers. A similar process is used in neon signs. Whenelectrified, a specific gas will produce a distinct color. Theultraviolet visible spectrometer detected hydroxyl signatures justafter impact that are consistent with a water vapor cloud in sunlight.

Data from the other LCROSS instruments are being analyzed for additional clues about the state and distribution of the material at the impact site. The LCROSS science team along with colleagues are poring over the data to understand the entire impact event, from flash to crater, with the final goal being the understanding of the distribution of materials, and in particular volatiles, within the soil at the impact site.

"The full understanding of the LCROSS data may take some time. The data is that rich," said Colaprete. "Along with the water in Cabeus, there are hints of other intriguing substances. The permanently shadowed regions of the moon are truly cold traps, collecting and preserving material over billions of years."

LCROSS was launched June 18, 2009 as a companion mission to the Lunar Reconnaissance Orbiter, or LRO, from NASA's Kennedy Space Center in Florida. After separating from LRO, the LCROSS spacecraft held onto the spent Centaur upper stage rocket of the launch vehicle, executed a lunar swingby and entered into a series of long looping orbits around the Earth.

After traveling approximately 113 days and nearly 5.6 million miles (9 million km), the Centaur and LCROSS separated on final approach to the moon. Traveling a fast as a speeding bullet, the Centaur impacted the lunar surface shortly after 4:31 a.m. PDT Oct. 9 with LCROSS watching with its onboard instruments. Approximately four minutes of data was collected before the LCROSS itself impacted the lunar surface.

Working closely with scientists from LRO and other observatories that viewed the impact, the LCROSS team is working to understand the full scope of the LCROSS data. LRO continues to make passes over the impact site to give the LCROSS team additional insight into the mechanics of the impact and its resulting craters.

What other secrets will the moon reveal? The analysis continues!

Jonas Dino
NASA Ames Research Center

Source:http://www.nasa.gov/mission_pages/LCROS ... sults.html

dwond
主序星
文章: 140
註冊時間: 週二 13 11月, 2007 11:51

文章 dwond » 週六 14 11月, 2009 04:42

More Images from the Preliminary Impact Results
11.13.09

圖檔
The visible camera image showing the ejecta plume at about 20 seconds after impact. The field of view of the spectrometers are indicated by the red circle.
Credit: NASA


圖檔
The view of the floor of Cabeus as seen through the LCROSS near-infrared camera. The fresh crater made by the Centaur impact is indicated.
Credit: NASA


圖檔
A zoom-in of the fresh Centaur impact as seen in the LCROSS near-infrared camera.
Credit: NASA


圖檔
All LCROSS instruments worked during descent with each one returning data at critical times. Shown here are the near-infrared downward viewing spectrometer and ultraviolet /visible spectrometer.
Credit: NASA


圖檔
Data from the down-looking near-infrared spectrometer. The vertical hashing on each data point (black dots) are error bars. The troughs and dips are the result of various compounds absorbing NIR light. These data are the average of spectra taken between 20 to 60 seconds after impact.
Credit: NASA


圖檔
Data from the down-looking near-infrared spectrometer. The red curve shows how the spectra would look for a "grey" or "colorless" warm (230 C) dust cloud. The smooth curve shows no compounds being absorbed.
Credit: NASA


圖檔
Data from the down-looking near-infrared spectrometer with a model that contains more compounds. A continued effort going forward will be to uniquely identify the various compounds responsible for the spectral features.
Credit: NASA


圖檔
The ratio of pre- to post-impact ultraviolet/visible light data. Each line shows a individual ratio of scans starting with earlier times (pre-impact) at the bottom, and later times, moving up. The general increase over time is the result of sunlight reflecting off dust grains in the ejecta cloud. The sharp vertical features which appear shortly after impact, indicated in the shaded blue area, are the emission lines associated with OH. The eight, or strength, of these lines are related to the amount of OH, and hence water, present in sunlight.
Credit: NASA


圖檔
The OH emission lines strength plotted as a function of time. Before impact the line is flat (no OH). After impact the line strength grows and remains above the pre-impact baseline for several minutes.
Credit: NASA


Source:http://www.nasa.gov/mission_pages/LCROS ... mages.html

回覆文章

回到「天文話題 Everything about Astronomy」

誰在線上

正在瀏覽這個版面的使用者:沒有註冊會員 和 8 位訪客