MESSENGER,Space ENvironment, GEochemistry and Ranging，Mercury surface, space environment, geochemistry and extensive explorationNASAThe exploration satellite launched on August 3, 2004 entered in 2011 to study the environment and characteristics of MercuryMercuryOrbit, Messenger is also the first human exploration of Mercury after Mariner 10 mission.
NASA"Messenger", a Mercury probe, was aboard on August 3, 2004Delta 2 carrier rocketstayFloridaCape CanaveralOfKennedy Space CenterWhen it was ignited and launched, Messenger began the planned exploration expedition, which took six and a half years and flew 7.9 billion kilometers.NASA's Messenger spacecraft has been orbiting Mercury for nearly four years. This is a long and fruitful journey, but the spacecraft will eventually run out of fuel.《New scientist》The magazine reported that scientists will light its booster for the last time on January 21, 2015, so that the detector can work at a sufficient height until March.But then, the detector will be very close to Mercury, which may cause some welding materials in its structure to melt.At that time, close-up shots will provide unprecedented views of Mercury's surface.For fun, the team is holding a competition to name the craters on the planet after famous artists。[1]
At 3:26 p.m. on April 30, 2015 (3:26 a.m. on May 1, Beijing time), Messenger ended its exploration mission by hitting Mercury, leaving an impact crater about 15 meters in diameter near the north pole of Mercury.[2]
Chinese name
Messenger
Foreign name
MErcury Surface, Space ENvironment, GEochemistry and Ranging
English abbreviations
MESSENGER
Detect target
Mercury
Task
Explore Mercury's environment and characteristics
Launch time
August 3, 2004
Launching country
U.S.A
Major manufacturers
Johns Hopkins University Applied Physics Laboratory
NASA's Messenger Mercury spacecraft took the Delta 2 rocket on August 3, 2004FloridaCape CanaveralOfKennedy Space CenterIgnite and lift off.The bright flame lit up the moonlit night sky and reflected on the Atlantic Ocean.The launch was a complete success, and Messenger began the planned exploration expedition, which took six and a half years and flew 7.9 billion kilometers.
NASACarnegieInstitute andJohns Hopkins UniversityJointly develop and undertake the responsibility of "Messenger" exploration spacecraftjohns hopkins university The applied physics laboratory is responsible for design and manufacturing.This is the first time in 30 years that a human probe has comprehensively orbited Mercury.
August 3, 2004 - launch;
August 2, 2005 - Flying over the Earth at an altitude of 2348km;
October 24, 2006 - Flying over Venus at 2987 km;
June 5, 2007 - Flying over Venus again at 338km;
January 14, 2008 - flew over the surface of Mercury at an altitude of 200km, and sent back the first batch of pictures of Mercury to the Earth;
Illustrate the Messenger task
October 6, 2008 - the second flyby of Mercury;
September 29, 2009 - flyby of Mercury for the third time at an altitude of 228km;
At 12:45 (UTC) on March 18, 2011, it entered the orbit of Mercury, becoming the first detector orbiting Mercury.[3]
US Eastern TimeAt 3:26 p.m. on April 30, 2015 (3:26 a.m. on May 1, Beijing time), Messenger ended its exploration mission by hitting Mercury, leaving an impact crater (about 15 meters in diameter) the size of an NBA basketball court near the north pole of Mercury.[2]
Structure introduction
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The basic components of the Messenger spacecraft include:
Science payload: Instrument used to collect scientific data of "messenger".
Sunshade: used to protect the spacecraft from direct sunlight, so that the electronic equipment and instruments of the spacecraft can operate normally even in the hot environment like Mercury.
Solar panel: Provide power for the spaceship."Messenger" also carries a battery, which can store the electric energy generated by the solar panel for use by other systems.
Booster: It can generate thrust by injecting fuel to change the orbit and posture of the spacecraft.
Booster rocket adapter: it is the contact point for spacecraft launch. When the "messenger" is separated from the booster rocket, the adapter will not work.
The scientific instruments carried by "Messenger" include:
Mercury Dual Imaging System: This is awide-angle lensAnd narrow angle lens camera, can monochrome, color and stereo imaging.
Gamma ray and neutron spectrometer: it will be used to draw the composition diagram of elements on the surface of Mercury.
X-ray spectrometer: It is also used to plot the element composition of Mercury's shell material.
Magnetometer: plot the detailed structure and dynamics of Mercury's magnetic field, and look for magnetized crustal rock areas.
MercuryLaser altimeter: used to measure the terrain of Mercury
Mercury atmosphere and surface synthetic spectrometer: measure the atmosphere of Mercury and find the mineral composition in the surface material of Mercury.
High-energy particleAnd plasma spectrometer: used to measure MercuryMagnetosphereComposition and characteristics of charged particles inside and around.
Unique design
NASA's request is to do more with less money.Therefore, "Messenger" must be impeccable in science and have lasting vitality. It has achieved the goals set by NASA by integrating existing technologies and effective engineering design:
Each important system of the spacecraft has a backup system. Once one system breaks down, another system (or backup system) can take over its task.
Messenger uses off the shelf components and standard data interfaces, reducing the need for unproven and expensive new technologies.
Messenger spacecraft adopts the design of other spacecraft subsystems for space exploration missions.
The antenna used is not deployable, but fixed, which reduces the possibility of losing contact with the earth control personnel during antenna deployment.
The ceramic material of the sunshade adopts the "passive thermal design", so the spacecraft does not need to be equipped with high temperature resistant electronic instruments.[4]
Carry scientific instruments
Mercury Dual Imaging System:wide-angle lensAnd narrow angle camera can be monochrome, color and stereo imaging.
Gamma rayGamma Ray and Neutron Spectrometer: it will be used to draw the composition diagram of elements on the surface of Mercury
X-ray apparatus(X-Ray Spectrometer): It is also used to draw the element composition of Mercury's shell material
MagnetometerMagnetometer: Draw the detailed structure and dynamics of Mercury's magnetic field, and find the magnetized crustal rock region
Mercury Laseraltimeter）: used to measure the terrain of Mercury.
Mercury atmosphere and surface combination detector: measure the atmosphere of Mercury and find the mineral composition in the surface material of Mercury.
High-energy particleEnergy particle plasma spectrometer: used to measure the composition and characteristics of charged particles in and around the Mercury magnetosphere
Technical difficulties
temperature control
As Mercury is very close to the sun, Messenger must withstand the test of high temperature and strong solar radiation when orbiting Mercury.To this end, mission planners specially built a "sunshade" for the "Messenger", that is, a heat resistant sunshade with high reflectivity.The researchers said that the sunshade installed on a titanium structure in front of the Messenger, about 8 feet high and 6 feet wide, could well protect the detector
When Mercury is closest to the sun, the temperature in front of the sun visor can reach 700 degrees Fahrenheit (371 degrees Celsius), but behind the sun visor, the temperature of Messenger and the instruments it carries remains at room temperature, that is, about 70 degrees Fahrenheit (20 degrees Celsius),
Precise measurement and control
It takes nearly 7 years for MESSENGER to enter the orbit of Mercury, and the whole journey is close to 8 billion kilometers. For such a long space and time distance, it is another problem that must be solved to do a good job of precise measurement and control of satellites.Academician of the Chinese Academy of Sciences, Chief Scientist of the Chinese Lunar Exploration ProjectOuyang Ziyuan: The distance is too far, but you must control its orbit very well so that it can detect according to the needs of scientists. Another problem is that precise measurement and control is necessary[5]
Reduce speed
Messenger traveled from the Earth to Mercury. Influenced by the solar gravity (potential energy is converted into kinetic energy), its speed is getting faster and faster. If it directly reaches Mercury, it will only take about three months. In order to use less fuel to reduce its speed, Messenger has flown about 7.9 billion kilometers in the flight time of six and a half years, made five orbital corrections, and more importantly, six flybys to the planets in the inner solar system,Slow down with a gravitational slingshot.
Even so, most of Messenger's weight is fuel, with a total weight of 1092 kg, of which 607 kg is fuel, accounting for 55.6%.
Undertake a mission
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Mercury is about 91 million kilometers away from the Earth. It takes only about three months for Messenger to fly directly to Mercury. In order to enter the orbit of Mercury, Messenger will first fly in the solar system for more than six years. The main reason is that in order to minimize the expenditure of space exploration projects, NASA cannot develop the detector too large and too heavy.If MESSENGER wants to directly enter the orbit around Mercury, it needs to carry more fuel, which means a carrier rocket with larger load and higher scientific research costs.
Due to the limitation of launch weight, Messenger failed to carry enough fuel to the sky.As a result, MESSENGER needs to make a long distance circumnavigation in the solar system for several years to slow down itself.After passing the Earth once, Venus twice and circling the sun for 15 circles, it will get enough gravitational support. When it flies over Mercury for the third time, because of the gravitational effect, Messenger will be violently thrown to Venus first, and then with the help of“slingshot effect ”, in March 2011, Earth time, it was bounced to Mercury again and smoothly "slid" into the orbit of Mercury, starting a one-year flight around Mercury;During this period, the seven scientific research instruments on the Messenger spacecraft will conduct a comprehensive exploration of Mercury's surface, space environment, geochemistry and space distance, and collect relevant data.
The Mercury orbit exploration project of Messenger is part of the "Discovery Plan" of NASA's ambitious planetary exploration series projects.For many years, the huge spending on space exploration in the United States and its practicability have been questioned by American taxpayers. NASA also took a lot of thought when applying for scientific research funding from the federal government. Therefore, when NASA officially launched the "discovery plan" for planetary exploration in fiscal 1994, it proposed that the policy of "faster, better, and more economical" should be adopted to require continuous scientific research with high concentrationAnd it doesn't cost too much money to solve many mysteries of planets in the solar system that are unknown to mankind.
Mercury
The National Aeronautics and Space Administration of the United States released the images and data taken by the Messenger spacecraft when it flew over the unknown surface of Mercury on February 1, 2008.Mercury is the smallest planet in the solar system and the planet closest to the sun.
Solomon, the chief researcher of the "Messenger" mission at the Carnegie Institution in Washington, said at the press conference: "This flight let us see the part of Mercury that the spacecraft had never seen before. Our small spacecraft has sent back exciting data like gold mine.
Some of the 1213 photos taken by NASA's Messenger probe were released on the 30th. They help support the view that Mercury is dotted with ancient volcanoes. As time goes on, the planet is shrinking, forming wrinkles like ridges. But other pictures are very surprising and puzzling.Mission Chief Scientist, Sean?Solomon said that the spider shaped landform captured in one of the photos "is different from what we see in other parts of the solar system." This picture shows a figure like a large meteorite crater, with many fuzzy lines extending around it.
Mercury is the planet closest to the sun, and people often compare it with the moon, which is the satellite of the earth.But these latest photos show the unknown side of Mercury. Through them, scientists learned about the colorful side of the planet. There was volcanic activity on it.With the help of NASA's constantly improving high-tech equipment, the photos taken by Messenger show light blue and dark red.Equipment scientist responsible for NASA's Messenger missionJohns Hopkins University Louis?Proctor said, "Mercury has clearly colored red and blue areas. It looks different from the moon
NASA says Messenger's instruments provide a crater on Mercury's dark sideTopographic contourTogether with other geological features, these features are unique in the solar system.
There are huge cliffs stretching hundreds of kilometers on the surface of Mercury, revealing the early stage of the planetHistorical faultThe type of activity,
NASA said that the spaceship also found another unique feature: more than 100 narrow and flat valleys radiated from the complex central area, which had never been seen before on Mercury and the moon, and scientists called it "spiders".
Aquidneck IslandBrown University Hyde, a co researcher of the scientific team, said: "There is a crater near the center of the spider, but it is still unclear whether the crater was originally formed or appeared later,
Messenger will fly over Mercury for the last time in 2011, and enter the orbit of Mercury for a year long research.Before that, it will fly over Mercury twice in October 2008 and September 2009.
Since its launch in August 2004, this spaceship has flown over the Earth once, and Venus will fly a total of 7.8 billion kilometers twice when it completes its six-and-a-half year exploration trip.
Messenger spacecraft flew over Mercury in the early morning of January 15, 2008, and its orbit was only about 200 kilometers away from the surface of Mercury when it was the closest.This is the second time that the human probe flew over Mercury after more than 30 years.On October 6, the second close flyby of Mercury took a large number of images of the surface of Mercury, and collected a series of scientific observation data. According to the news released by NASA, Messenger took more than 1200 images during the entire flyby, and its orbit was only about 200 kilometers away from the surface of Mercury when it was the closest. It is estimated thatUS Eastern TimeThe images and data sent back by the Messenger can be received in the early morning of the 7th.According to experts from NASA, Messenger's mission to Mercury is to find answers to six major questions.Breaking these doubts will not only help to study Mercury, but also promote scientists to have a deeper understanding of the Earth, etcterrestrial planetThe formation and evolution of.
Solve many mysteries of Mercury
1. Mercury's density
Mercury is similar in volume to the moon, but its density is much larger than the moon, only slightly lower than the earth, and it ranks second among the earth like planets in the solar system.Without the compression of the planet's own gravity on the interior, Mercury would be more dense than Earth.According to its density, scientists once speculated that 65% of Mercury is a core rich in iron and other metals, which is about twice the proportion of Earth.The various spectrometers carried by Messenger can measure the composition of elements on the surface of Mercury, and the results are expected to be used to verify various theories about the density of Mercury.
2. The geological history of Mercury
In 1974 and 1975, the American "Mariner 10" spacecraft took photos of 45% of the surface area of Mercury. The surface of Mercury in the photos is old and full of pits, which is quite similar to the surface of the moon.However, the photos taken by Mariner 10 did not provide enough details about the formation mechanism of Mercury's surface,
The instruments on Messenger can photograph the entire surface of Mercury and analyze the mineral and element composition of the rocks on its surface. Scientists hope to determine the sequence of various geological processes that shape the surface of Mercury on this basis.
3. Mercury Core Structure
Mariner 10 accidentally discovered that Mercury has a magnetic field distributed throughout the planet.In otherterrestrial planetOnly the Earth has the same characteristics.The earth's magnetic field is believed to be formed by the movement of liquid magma in the outer core. Mercury, which is much smaller than the Earth, should have cooled down and solidified completely long ago.The current Mercury magnetic field is the remnant of the planet's early primitive magnetic field, or is it said that the Mercury core is not completely solid, which led to the formation of the magnetic field. The study of Mercury core structure by Messenger will help to better explain how Earth like planets generate magnetic fields.
4. Magnetic field characteristics
The Earth's magnetic field will respond to solar activities such as solar wind and solar flares, often producing highly dynamic changes.Mariner 10 once found that Mercury's magnetic field would have similar dynamic changes, but the detection results of the spacecraft failed to reveal the characteristics of Mercury's magnetic field.Messenger will use a magnetometer and other magnetometers to carry out a long-term detailed observation of Mercury's magnetic field, and then determine the strength of Mercury's magnetic field and its change law.
5. Polar ice
Mercury is the closest to the sunSolar system planetsThe surface temperature can reach up to 450 ℃, but its two poles are hugeCraterInside, the sun never shines. The constant temperature is below minus 212 ℃.In 1991, scientists found for the first time that the inner side of the polar craters of Mercury has strong reflective ability according to radar observation images. The most common view is that there is ice in these areas.One of the missions of Messenger is to check whether there is ice on Mercury,
6. Volatiles of Mercury
Mercury has an extremely thin atmosphere. There are six known elements in the atmosphere of Mercury, including hydrogen, helium, oxygen, sodium, potassium and calcium. These elements are believed to come from various channels and enter the atmosphere of Mercury in different ways.Messenger will use a variety of spectrometers to study the composition of Mercury's atmosphere and determine how various molecules are generated
7. What's behind Mercury
NASA's“Mariner 10 ”It is the only spaceship that has ever explored this mysterious world in the solar system.But it only captured images of less than 45% of Mercury's surface (a crater terrain).This means that we know almost nothing about half of the planet except for a few observations made by radar on the ground. Hopkins Mountain, ArizonaMulti mirror telescopeThe director of the observatory, Faith Vera, said, "We can't be too confident about what the other side of Mercury looks likecelestial bodies It looks very different from the other one.We are looking forward to the great surprise from the other side of Mercury. "
8. Mercury has ice on the side near the sun
Messenger Mercury probe
On the side of Mercury closest to the sun, the temperature can reach more than 800 degrees Fahrenheit (425 degrees Celsius), which is really shocking when there is ice in this environment.For radar, ice is more reflective. According to the ground radar, there may be frozen water deposits in the deep dark craters where the polar regions of Mercury will never receive sunlight.This water may come from the internal gas of Mercury, or from the water vapor generated when meteorites collide.The Messenger spacecraft will search for hydrogen at the bottom of the polar crater, which is always in the dark on Mercury.If the spaceship can find hydrogen, it may have found ice in the world like hell.
9. Mercury is shrinking
As Mercury's core freezes, the planet may be shrinking.“Mariner 10 ”The photos taken by the spacecraft show that there seems to be wrinkles extending from the inside on the surface of Mercury, leading to a huge cliff 1 mile high and hundreds of miles long on Mercury. The "Messenger" spacecraft will pay attention to such wrinkles on the back of Mercury and study its metal core by analyzing the planet's magnetic field.
10. Mercury has a melting asteroid in its orbit
Scientists do not know whether there is a group of objects called "Zhurong Asteroids" located inside the orbit of Mercury, hidden in the dazzling sunlight?Although the Messenger spacecraft has very limited opportunities to detect these asteroids during its approach to Mercury, it still has a chance to detect these asteroids.In order to avoid being dried by the sun, Messenger will always hide in the sunshade facing the sun, and the scientific instruments on the spacecraft will be far away from the sun.Sean Solomon, the main investigator of the Messenger mission, said that scientists will also use the Messenger to "find any clues that there may still be modern melting asteroids.",
11. Where does Mercury's atmosphere come from
Mercury's incredibly thin atmosphere is very unstable and often escapes from the planet's weak gravity.Scientists do not yet know where Mercury's atmosphere is constantly replenished.Researchers suspect that the hydrogen and helium in Mercury's atmosphere are constantly brought here by the solar wind (the flow of charged ultrasonic particles emitted by the sun).Other gases may have evaporated from the surface of Mercury, or seeped from the interior of the planet, or may have been brought by evaporated meteorites.Vera said that Messenger will make a close observation of the planet's atmosphere to find out how the atmosphere of Mercury is generated,
12. Why Mercury has magnetism
“Mariner 10 ”One completely unexpected discovery was that Mercury has a magnetic field.Theoretically, only when a planet rotates rapidly and has a molten core can it generate a magnetic field.However, it takes 59 days for Mercury to rotate once, and it is so small, only about one-third of the earth's volume, so its core should have cooled long ago.To solve this mystery, Messenger will probe Mercury's magnetic field.Some astronomers believe that the planet's magnetic field has been static, but a few years ago scientists found that Mercury seems to have a molten core, so the planet can still effectively generate magnetic fields.
13. Why Mercury has such high metal content
Mercury is extremely dense, so researchers estimate that the iron rich core of this planet may account for nearly two-thirds of the weight of the entire star. This is a surprising figure, twice the weight of Earth, Venus or Mars.In other words, the core of Mercury may occupy three quarters of the planet's diameter.One explanation for this unusual density is that during the violent collision billions of years ago, the original appearance of Mercury was stripped off. This collision also moved Mercury to the sun and reached its position.Another theory shows that Mercury was formed at this location. In order to find out which of the two theories about the origin of Mercury is more correct, the small scientific instruments of Messenger will detect the geological conditions of the planet.Understanding the formation process of Mercury will help astronomers to further understand the evolution process of planets.
Reach Mercury
5. NASA's Messenger probe began to implement a series of Mercury orbit braking actions, and successfully entered the orbit of Mercury on March 17, 2004.This is the first time in the history of human spaceflight to successfully send a probe into orbit of Mercury.MESSENGER is the abbreviation of "Mercury Surface, Space Environment, Geochemistry, and Ranging", which means "Mercury Surface, Space Environment, Geochemistry, and Omnidirectional Telemetry".
NASA Administrator Charles Bolden said: "This mission will continue to bring us the latest data on Mercury in the next year."MarylandThe control center of the Messenger spacecraft at the Johns Hopkins University Applied Physics Laboratory.At this time, engineers are busy receiving the measurement and control data sent back by the detector, so as to confirm that the detector has entered the orbit correctly."NASA's exploration program is constantly rewriting our textbooks, and the Messenger program is the best example of our continuous efforts to expand the frontiers of human knowledge," he said
US Eastern TimeAt 21:10, Messenger had shut down its recoil engine according to the established procedure, and the probe had successfully entered the orbit around Mercury, but engineers still needed to wait for the probe to send back more accurate data.10: 45, MessengerHigh gain antennaPoint to the earth and start transmitting data.After analysis, the ground control engineers officially announced that the MESSENGER detector had successfully completed the track braking and successfully entered the orbit of Mercury without any abnormality
During braking, the main engine of Messenger ignited for about 15 minutes to slow down the spacecraft, so that it was captured by the gravity of Mercury and entered orbit.This action took place in the deep space about 96 million miles away from the Earth.
"This is the biggest milestone since the launch of Messenger almost six and a half years ago," said Peter Bedini.He comes from the Applied Physics Laboratory and is the project manager of Messenger.He said, "This achievement is the result of the hard work of all project team members. The members of navigation control, flight guidance and other teams are very impressive. It is they who ensure that the probe can travel 4.9 billion miles (7.886 billion kilometers) and reach Mercury safely,
In the next few weeks, the engineers of the Applied Physics Laboratory will work hard to ensure that the spacecraft systems are in good working condition in the harsh environment near Mercury.Various instruments on the spacecraft will be turned on for inspection, and the Messenger probe will officially start scientific exploration.
"Although it is not far from the earth, Mercury exploration has been a blank in the past decades," said Sean Solomon, who is from the Carnegie Institution in Washington and is the chief scientist of the Messenger project. "This is the first time in history that we have set an observatory in the orbit of a big planet at the innermost side of the solar system.We will try to reveal the secrets of Mercury, and the latest data about it will help us better understandterrestrial planetThe formation and evolution mechanism of,
The last and only exploration of Mercury was in 1974, when the United States“Mariner 10 ”The probe flew over Mercury at close range, but could not enter orbit due to technical reasons.
The Johns Hopkins University Applied Physics Laboratory (APL) designed and built the Messenger spacecraft.The laboratory is also responsible for the operation and management of the spacecraft entrusted by the NASA Science Mission Board.
NASA(NASA) On March 30, the first pictures sent back by the spaceship Messenger were released, which was the first time that the surface of Mercury was photographed by a spaceship in orbit of Mercury.According to the survey data, the temperature difference between day and night of Mercury exceeds 570 ℃.Scientists expect spacecraft to find water on Mercury in missions at least one year in the future.Mercury is the closest planet to the sun in the solar system.After six and a half years of flying for 7.9 billion kilometers, Messenger finally entered the orbit of Mercury on March 17, and sent back hundreds of the first pictures of Mercury
Machout crater is about 100 kilometers in diameter. This photo was taken by Messenger on October 6, 2008.NASA said: "At 5:20 this morning, Messenger captured the historic picture of Mercury, which is the first time that a spacecraft has obtained the image of Mercury in orbit,
The Messenger took six hours to take 363 pictures.According to the photo released by NASA, the first photo shows a special black crater named "Debusi" at the top, and the south pole near Mercury at the bottom. No spacecraft has ever seen this area in the past,
Of particular interest is the crater shadow at the north and south poles of Mercury.Since the sun cannot shine on the polar regions, scientists expect Messenger to find frozen water there,
The picture is marked with some MercuryMeteorite crater。Mercury's surface temperature is extremely extreme. During the day, metals such as tin with a melting point of 232 degrees and lead with a melting point of 327 degrees will become liquid on the surface of Mercury;At night, the temperature drops to minus 148 degrees Celsius, and the temperature difference between day and night is 574 degrees.
Mission spokesman Sean Solomon said: "The first batch of images sent back by Messenger and the first-hand measurement data obtained by its equipment are just beginning to expect that more new information will be imported in the next few years,
Mariner 10 in the pastspacecraftHe flew over Mercury twice in 1974 and 1975, and took photos in the distance when he flew over. "Messenger" took photos in the orbit closest to the surface of Mercury 200 kilometers away. Next, Messenger will begin to orbit Mercury for at least a year
The picture shows the surface area of Mercury that has never been seen before. The Messenger probe with a camera took this picture at an altitude of 450 kilometers. A collision outside the picture area produced secondary craters all over the field of vision, some of which formed strange chains,
Into orbit of Mercury
After about six and a half years of flight, NASA's Messenger Mercury probe finally entered orbit around Mercury, becoming the first probe ever to enter orbit of Mercury despite the launch of NASA“Mariner 10 ”The probe flew by Mercury from 1974 to 1975 and took some pictures. Astronomers have been studying these pictures for decades, but Mariner 10 did not take a full picture of Mercury. Messenger will fill these gaps.During the one-year observation, the probe will conduct detailed mapping of the surface of Mercury, and study its composition, magnetic environment, thin atmosphere and other characteristics.[6]
Exploration achievements
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Mercury or water ice
The bright deposits in Mercury's dark zone may be water ice
According to data obtained by NASA's Messenger probe, Mercurypolar regionThere may be water ice in the depth of the permanent dark area crater in the region.Mercury is the innermost planet in the solar system, with a surface temperature of more than 400 degrees Celsius.Scientists have long suspected that the bright sediment found in radar scanning may be the data sent back by the water ice Messenger, which further enhances the credibility of this view.
Nancy Chabert, the scientist in charge of the Messenger imaging system and the laboratory of applied physics at Johns Hopkins University in the United States, said, "Before that, we had never obtained images of the areas where these bright sediments are located. Mercury Dual Imaging System (MDIS)The images taken show that all the bright sediments near the south pole of Mercury are located in the permanently dark area, and the bright sediments near the north pole are also located in the dark area, providing evidence for the water ice hypothesis. "
But Chabert also pointed out that this discovery is not conclusive evidence, proving that these sediments are water ice.It is found that the temperature of these bright sediments in the crater is relatively high, which requires a thermal insulation layer to allow the existence of water ice.Scientists are analyzing the relevant data.Messenger entered the orbit of Mercury in March 2011 and orbited Mercury for two times a day. It has taken nearly 100000 photos and made more than 4 million measurements on the surface of Mercury.Messenger spent six years flying 60 million miles (about 96.56 million kilometers) before entering the orbit of Mercury.
A crater on Mercury may be related to orbital instability
In two papers published in the journal Science, the researchers detailed their findings.Co author of research paperMassachusetts Institute of TechnologyMaria Zubor, a professor of earth geography at the University of California, said: "Before the comprehensive observation of Messenger, many scientists believed that Mercury was very similar to the moon and calmed down very early in the history of the solar system. For most of its evolutionary history, it was a 'dead star'.Now, we have found strong evidence to prove that there is a different dynamic phenomenon inside Mercury, indicating that Mercury was active for a long time. "
According to the gravity measurement data of Messenger, the research team speculates that Mercury may have a huge iron core, accounting for nearly 85% of the radius of Mercury, and the mantle and crust only account for 15%,Just like David Smith, a scientist at the Goddard Space Flight Center of the Space Agency, said: "We have put forward an idea about the internal structure of Mercury before, but the initial observation data did not support our theory and led us to doubt the observation results.Later, we carried out more research, confirmed the accuracy of the observation results, and then re studied the theory of Mercury's internal structure, which is consistent with the observation results
Using the laser measurement data on the surface of Mercury, researchers have mapped many geomorphic features in the northern hemisphere of Mercury, and found that the altitude change is smaller than that of Mars or the moon.In addition, they also found the largest crater of Mercury in the Canollis Basin of Mercury, which greatly surprised them.The bottom part of the crater is higher than the edge, indicating that the force from the inside of Mercury pushed the crater higher after its formation.Zuber and his colleagues also found an area composed of lowlands, almost centered on the north pole of Mercury.According to their research, this low region gradually migrated to this region during the long evolution of Mercury.
New findings
Research shows that there may be a huge magma ocean on the surface of Mercury 4.5 billion years ago
Mercury Past Surface Imagination
According to foreign media reports,Massachusetts Institute of TechnologyThrough the analysis of the chemical composition of Mercury's rocks, scientists found that this planet may have a huge magma ocean in the past. The time point was 4.5 billion years ago. This new research task was completed by the Messenger probe, which aims to analyze the surface of Mercury, the space environment, and the composition of planetary chemical substances.Since March 2011, NASA's probe has begun to collect relevant data. A group of scientists are responsible for analyzing the X-ray fluorescence spectrum data. This task has collected the composition of the rocks on the surface of Mercury. Scientists hope to reveal what geological process happened to Mercury, leading to two different types of rocks on its surface?
In this regard, scientists created two types of rocks in the laboratory to simulate the geological evolution process under the high-temperature and high-pressure environment. Through experimental scientists, they imagined that there had been a huge magma ocean on Mercury. In this environment, two different types of rocks could be evolved, which existed on the surface of Mercury again through the mechanism of lava eruption through crystallization, solidification and finally.according toMassachusetts Institute of TechnologyTimothy Grove, a geology professor, said: "The events on Mercury are actually very amazing. The age of the crust is probably over 4 billion years old, so these magma oceans should exist in the very old past,
In order to answer this question, the research team of Massachusetts Institute of Technology in the United States used the composition data obtained by the detector to prepare and synthesize these two types of rock in the laboratory, and simulated these two types of synthetic rocks under high-temperature and high-pressure environment to experience various geological processes.Through these experiments, scientists found that only one mechanism could explain the observed phenomenon, that is, there was once a huge magma ocean, which formed two different layers of crystal layers and gradually condensed, then melted again into magma and ejected to the surface of Mercury.
Messenger status
NASA's Messenger spacecraft has found signs of seasonal changes on Mercury, and it has found what was previously thought to be more abundantHeavy metal elementsThe Iron Messenger probe made this observation when it flew past Mercury for the third time on September 29, during which it obtained a lot of measurement data and took many pictures of the concealment on the surface of Mercury and the atmosphere.Due to the impact of data failure on the spacecraft during overflight, only half of the planned survey work has been carried out. Earth exploration
The $446 million probe flew over Mercury for the third time, within 142 miles (228 kilometers) of the planet's surface.More unknown areas have been observed during this flyover, and 98% of theTopographic Map of Mercury Surface。The purpose of this flyby is to use Mercury's gravity to change the operation route of Messenger, so that it can enter the orbit of Mercury in about 2011,
Thin atmosphere
Scientists call Mercury's atmosphere "exosphere", which is composed of atoms raised from the surface of Mercury.Mercury's atmosphere is very thin, and its density is very small, which means that the atoms in the atmosphere can rarely collide.It also has a small tail extending outward from the planet in the opposite direction to the sun. During the three flyovers, Messenger mainly looked at the differences of three kinds of atoms in the atmosphere of Mercury -- sodium, calcium and magnesium. Scientists found that the atmosphere of this planet contained less sodium atoms when it flew over Mercury for the third time than when it flew over Mercury for the second time,
Mission scientist Ronald Vervack said: "This is an exciting moment, and this discovery is completely unexpected" because when Mercury moves along the solar orbit, the radiation pressure generated by the sun on it will constantly change, which changes the number of sodium atoms released from the surface of Mercury.Vilvac said that Mercury's atmosphere is affected by seasons during its orbit.The change of calcium and magnesium atoms in "each season" is smaller than that of sodium atoms, which shows that different atoms "have their unique seasonal changes".
Understanding these seasonal differences will help scientists understand how the surface material of Mercury is lost and how the surface of the planet changes over time.John, Maryland, USA.johns hopkins university Vilvack of the Applied Physics Laboratory said that the atmosphere of Mercury is "the final product of these processes for hundreds of millions of years, and these processes have never stopped".
Unexpected discovery on the surface of Mercury
Messenger's flyby of Mercury also provided scientists with first-hand direct observation data on the amount of specific elements on the planet's surface.For a long time, scientists have judged that the surface of Mercury is lack of iron and titanium based on early observation dataHeavy metal elementsThey think the planet'sGrey cast ironThe nuclear mass is 60% of the total mass of Mercury, and it is believed that Mercury is the most compact in the solar systemRocky planet
The observation data of Messenger show that there are a lot of such elements on the surface of Mercury, and their concentration is almost the same as that of the lunar perigeemare basalt The concentration of these substances in (nearby maria basalts) is similar, which means that the model of the formation and evolution of the planet must be modified. David Lawrence of the Johns Hopkins University Applied Physics Laboratory said: "For us, this is a very shocking result"
The third flight also captured the surface map of the unknown area.The high-definition color pictures taken by the spacecraft's cameras and instruments also show the other 6% of the planet's surface topography that has never been observed close before.Brett Denevi, an imaging research team member and postdoctoral researcher at Arizona State University Tempe, said: "Our work is helpful for mapping the entire surface of Mercury."
The pictures taken during this flyby show the surface features of Mercury, which we have seen before, but the previous data are not detailed enough to draw the surface map.It can be seen from the figure that the area around an irregular low-pressure area is obviously very bright. Its walls are steep and the shape is very strange. Deniev said, "All these are the characteristics of volcanic craters." Other pictures show a double ring impact basin with a diameter of about 180 miles (289.68km). The characteristics of this basin are similar to that of RaditladiThe characteristics of the basins are very similar.In 2008, when MESSENGER flew over Mercury for the first time, it observed the Radteladi Basin,
De Neville said, "One of the similarities is that the age of the Radteladi Basin is very similar to it. It is estimated that the basin is about 1 billion years old, which is not a big age for the impact basin, because most of the basins are about four times older than it. The inner wall of the basin is even younger than the basin itself, and it is different from the surrounding color.We may have found younger volcanic material on Mercury. "
Messenger needs to travel 4.9 billion miles (7.89 × 1012 meters) to enter the orbit of Mercury, and now it has completed nearly three quarters of the journey.The whole process includes 15 circles around the sun. In addition to flying over Mercury, Messenger also flew by the Earth in August 2005, and passed near Venus in October 2006 and June 2007,
Recently, scientists analyzed the observation data of the Messenger probe's third flight over Mercury in 2009, and the latest results found the youngest signs of volcanic activity on the surface of Mercury, as well as the latest information on magnetic substorms, and the first occurrence of ionized calcium in Mercury's ultrathin outer atmosphere.The research report was published on the website of Science Journal published on July 15.
The youngest evidence of volcanic activity
Sean Solomon, chief investigator of MESSENGER, said: "Every time MESSENGER flies over Mercury, it will get new discoveries! We find that Mercury is a very dynamic planet, and its activity runs through the whole historical stage." In the previous two surveys, MESSENGER found that volcanic activity was widespread in the early historical period of Mercury,In the latest survey of the third flight over Mercury, the detector found a circular collision crater with a diameter of 290km, which is the youngest crater structure on the surface of Mercury observed so far. Scientists named it "Rachmaninoff", and its bottom has a very smooth plain.
Louise Prockter, of Johns Hopkins University Applied Physics Laboratory, said: "We believe that the plain at the bottom of Rachmaninoff crater is the youngest volcanic sign found in Mercury so far.In addition, we found diffuse ring-shaped bright materials around irregular depressions in the northeast of Rachmaninoff crater, which indicates that these irregular depressions are volcanic vents, and their diameters are larger than those of volcanic vents previously surveyed.This observation suggests that the volcanic activity on the surface of Mercury is more persistent than previously thought, perhaps until the second half of the solar life history.
Magnetic substorm
Magnetic substorm is a kind of space weather, which has appeared intermittently on the earth, usually several times a day, lasting for 1-3 hours.The magnetic substorms on the earth are often accompanied by a series of special phenomena, such as the magnificent auroras over the Arctic and Antarctic.Magnetic substorms are also accompanied by dangerous energy particles, which will lead to catastrophic accidents of Earth observation satellites and ground communication systems, especially in the geosynchronous orbit region.The energy of the geomagnetic substorm comes from the magnetic energy at the tail of the geomagnetic field.
When the Messenger probe flew over Mercury for the third time, the magnetometer loaded by the probe found for the first time that the magnetic energy in the tail of Mercury's magnetic field was "loaded" like a substorm. The energy of this Mercury magnetic substorm was about 10 times that of the Earth's magnetic substorm, and its operating speed was 50 times that of the Earth's magnetic substorm.
James A. Slavin, a space physicist at NASA's Goddard Space Flight Center, said that the latest observations show that the relative intensity of Mercury's magnetic substorm is greater than that of the Earth's magnetic substorm. At the same time, we also found that the tail enhancement of Mercury's magnetic field is consistent with the Dungy cycle, which is an indicator of the plasma cycle in the magnetosphere.
Slevin said: "The latest observation of the Messenger probe shows for the first time that the duration of the substorm can be determined by the Tanggi plasma cycle time on another planet outside the Earth, which suggests that this feature of the Earth's magnetosphere is a universal phenomenon in the universe.
Composition of Mercury's outer atmosphere
The outer atmosphere of Mercury is very thin, which is composed of atoms and ions on the surface of Mercury and in the solar wind. The observation of the outer atmosphere of Mercury by Messenger will provide an opportunity to study the interaction between the surface of Mercury and its space environment, and can detect the composition of the surface of Mercury,The material lost by the planet to the galactic space will help scientists understand the current and historical composition of Mercury.
The observation results of MESSENGER probe on Mercury's outer atmosphere show the unique spatial distribution characteristics of neutral and ionized elements in the outer atmosphere. The third overflight survey first detected the composition of Mercury's south pole and north pole outer atmosphere.Ron Vervack, of Johns Hopkins University Applied Physics Laboratory, said, "The survey shows that the outer atmosphere of Mercury contains sodium, calcium and magnesium. In this flyover survey, Messenger first found that the outer atmosphere contains ionized calcium，[7]
End the mission
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Photos taken by Messenger before the last orbit correction
3900 days ago, NASA launched the Messenger probe to visit the planets in the inner solar system;Four years ago, MESSENGER finally reached its destination and entered the orbit of MercuryMariner 10 Then the first probe to visit Mercury at close range.It collects a lot of data about Mercury.After the fuel runs out, it will crash on the surface of Mercury at 19:26:02 UTC on April 30 and UTC+8 Beijing time (3:26 May 1).[8]
At 3:30 on April 30, 2015, the Messenger probe ended its mission and hit the ground at 3.9km/s by hard landingMercurySurface.It is expected that a crater with a diameter of 16 meters will form on the surface of Mercury. In the last days, it is still sending back high-resolution photos.The new probe will arrive in 2024, when we can see the image of the impact crater.[7]
Other information
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1. A marathon runner
The distance between Mercury and the Earth is not very far, but in order to enter the orbit of Mercury, Messenger needs to slow down significantly, so since its launch in 2004, Messenger has flown over Venus, the Earth and Mercury several times to slow down.When it entered the orbit of Mercury, the Messenger probe had already flown about 7.9 billion kilometers,
2. Sprinter
Although the journey was long, Messenger's flight speed was not slow.In six and a half years of space flight, the average speed of Messenger relative to the sun has reached about 136000 kilometers per hour, which is almost five times that of NASA's space shuttle in low Earth orbit.Sometimes, Messenger will fly at a speed of about 225000 kilometers per hour, close to the fastest flight speed of the probe in history.
3. A "oil tiger"
When it was launched in 2004, the weight of Messenger reached about 1100 kg, and the proportion of propellant accounted for 55%, reaching 600 kg.
4. The body is not huge
The main body of "Messenger" is about 1.42m high, 1.85m wide and 1.27m long. Its volume is equivalent to a large desk. It is equipped with two solar panels with wings of an area of about 1.5m * 1.65m, which are spread on both sides of the detector.[9]
5. High tech equipment
If you travel a long distance to Mercury, of course, you should do a good "reconnaissance". Good equipment is essential.Messenger carried seven different scientific instruments and one radio scientific experiment equipment.
6. "Messenger" has a sunshade
Because Mercury is very close to the sun, Messenger must withstand the test of high temperature and strong solar radiation when working. Therefore, it was equipped with a sunshade, that is, a heat resistant sunshade with high reflectivity.
7. The task duration is only "2 days"
Although MESSENGER is ambitious, its mission lasts only two Mercury days. Mercury rotates slowly. One Mercury day is equivalent to 176 Earth days.Compared with its rotation, Mercury orbits the sun at an extremely fast speed, and can run for one cycle in just 88 days.Therefore, Messenger will experience two Mercury days, but more than four Mercury years during the 12 month Earth observation in orbit.
8. Be generous
Messenger doesn't have enough fuel to help it return to Earth, so after the exploration mission, Mercury, the planet he loves to explore all his life, will become the final destination of Messenger, and it will eventually fall to Mercury.[10]
