when did nasa's mariner 10 visit mercury

The first mission to employ gravity assist, or using the gravity of a planet to alter a spacecraft's speed and trajectory to fly by its target planet, the Mariner 10 mission flew by both Venus and Mercury, snapping photos and collecting data.

Mission Statistics

Launch Date

Nov. 3, 1973

About the mission

The first mission to employ gravity assist, or using the gravity of a planet to alter a spacecraft's speed and trajectory to fly by its target planet, the Mariner 10 mission flew by both Venus and Mercury, snapping photos and collecting data.

Also the first spacecraft to visit Mercury, a feat that wouldn't happen again for more than 30 years, Mariner 10 data revealed a surprising magnetic field and a metallic core comprising about 80 percent of Mercury's mass.

Instruments

• Imaging system
• Electrostatic analyzer
• Electron spectrometer
• Triaxial fluxgate magnetometer
• Extreme ultraviolet spectrometer
• Infrared radiometer

Mariner 10: First Mission to Mercury

Mariner 10 was the first spacecraft to visit Mercury. It showed close-up pictures of the sun's closest planetary neighbor and also did investigations of Mercury's environment and surface.

The spacecraft had other, lesser-known milestones as well. It was the first spacecraft to slingshot past one planet on its way to visit another. Mariner 10 was also the first probe to visit two planets in one mission.

Despite several mechanical problems during the mission, NASA persevered and got a lot of science out of the struggling spacecraft. Mariner 10 thus became a demonstration of how to adapt missions on the fly, which is an important skill NASA still uses today. The plucky spacecraft even has a postage stamp to commemorate the mission.

Interplanetary mystery

When Mariner 10 lifted off from Cape Canaveral on Nov. 3, 1973, very little was known about our neighbors in the solar system. Mariner 10 would only have quick flybys past Venus and Mercury, to be sure. But there was a lot that could be glimpsed even in a short span of time.

Astronomers were curious about Mercury's high density, and what lay inside the planet's core . The running hypothesis, according to NASA, was that the planet's density was due to a high concentration of metals. But there were questions about the exact composition of the core, and how that core was put together during the early days of Mercury's formation.

As for Venus, scientists wanted to delve deeper into how the planet interacted with the solar wind. On Earth, the magnetic field buffers us from particles streaming out from the sun . The sun's energy, when it hits Earth, forms a shockwave. Some particles flow along magnetic field lines and form auroras at the Earth's poles. On Venus, though, scientists didn't fully know how the sun's particles affected that planet.

Mariner 10's mission would, with any luck, shed some light on these mysteries. The spacecraft cost $100 million in 1973 dollars, the equivalent of more than half a billion dollars in today's money. Many scientists' hopes were riding on the 1,045-pound spacecraft.

Troubles en route to Venus

Mariner 10 kept spacecraft planners busy as it moved toward a planned rendezvous with Venus. NASA needed not only to keep the spacecraft healthy, but also to make sure it was on the right trajectory to slingshot around the planet to make it to Mercury.

It was only a three-month trip to Venus, but it probably felt like a lot longer to the people managing Mariner 10 through various mechanical difficulties. Shortly after launch, NASA discovered that some television camera heaters were not turned on. Mission control sent a command to deactivate and then reactivate these heaters, but was not successful. Luckily for NASA, the camera temperature stabilized before it got too cold to operate.

There was a backup spacecraft available to launch if the cameras became too cold. But that would have been an expensive solution.

Science experiment issues were not the only problems besetting Mariner 10 as it flew toward Venus. The flight data system kept resetting itself. In January, the spacecraft switched itself to a standby power system, an error that couldn't be reversed.

Communications and data transmissions became rocky when the high-gain antenna developed some problems. Worse, Mariner 10 also lost 16 percent of its attitude control fuel on Jan. 28 in one spectacular purge caused by a mechanical problem.

"The spacecraft seemed to be behaving quite neurotically and confounding its designers and controllers," a NASA historian wryly wrote in "The Voyage of Mariner 10."

Controllers went to a backup option to align Mariner 10 for its scoot by Venus, and succeeded in performing the slingshot. The video camera heaters resurrected around this time, providing another bright spot in an otherwise tumultuous few months. Mission controllers elected not to use the heaters for the time being, as the heat from the sun was enough to keep the cameras functional.

Glimpses of Venus

Mariner 10 gave scientists a much better understanding of how Venus' magnetic field performs. As it turned out, the planet only had a twentieth of the strength of Earth's magnetic field , according to Mariner 10 measurements. This means it can't shield Venus to the same extent that we see here on Earth. For example, the large clouds of particles seen in Earth's radiation belts don't congregate near those of Venus.

The spacecraft also measured a bow shock of radiation as the solar wind hit the area around Venus, which was seen before with the Mariner 5 and the Soviet Union's Venera 4 spacecraft. At the time, though, scientists didn't quite understand how this was happening.

Mariner 10's visible light pictures of Venus didn't show much variation, which proved the planet was socked in by a thick cloud layer . In ultraviolet light, though, the spacecraft could see swirls and patches. Venus apparently had an active atmosphere.

The spacecraft was well on its way to Mercury now, but it continued to cause headaches for the engineers back on Earth. On Feb. 18, 1974, the spacecraft got confused between a bright particle and its navigation star, Canopus .

Controllers had seen this problem since launch, but on this particular occasion the spacecraft was confused for nearly two hours and spent valuable fuel. The Canopus problems increased to 10 a week by the end of that month, from perhaps one or two a week in the time after launch.

Mercury at last

The efforts of Mission Control weren't in vain, though. Mariner 10 made it past Mercury on March 29, 1974, the first of three passes. (The other two were on Sept. 21, 1974, and March 16, 1975.)

Mariner 10 showed a bleak planet that looked similar to the surface of the moon . Craters and bare ground showed up in the pictures. One significant difference was the presence of scarps, which to scientists suggested that the planet's crust might have shrunk at some time during its history.

Another surprise came when Mariner 10 took measurements of the magnetic environment around Mercury. The instruments showed that Mercury had a small magnetic field that is about one-sixtieth as strong as that of Earth's. Scientists believed that Mercury's magnetic field came from within the planet rather than being generated through the planet's interaction with the solar wind.

Mariner 10 detected a faint helium atmosphere around the solar system's innermost planet. Also, the spacecraft was used to test out new navigational techniques that mission planners would be able to use on future spacecraft.

The aging spacecraft had several other difficulties during the later passes, including losing much of its attitude gas in attempts to lock on to Canopus. NASA continually had to make changes to Mariner 10's mission to get the most science out of the spacecraft's passes by the closest planet. But it showed us quite a bit despite its problems.

NASA commanded Mariner 10 to turn off its transmitter on March 24, 1975, after the spacecraft ran out of fuel. Today, Mariner 10 is still presumably orbiting the sun, but we haven't heard anything from the spacecraft since then.

Despite Mariner 10's troubles, a lot of science was performed. It provided the only glimpse of Mercury we would see for a generation, until the MESSENGER spacecraft flew that way for the first time in 2008.

— Elizabeth Howell, SPACE.com Contributor

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Elizabeth Howell (she/her), Ph.D., is a staff writer in the spaceflight channel since 2022 covering diversity, education and gaming as well. She was contributing writer for Space.com for 10 years before joining full-time. Elizabeth's reporting includes multiple exclusives with the White House and Office of the Vice-President of the United States, an exclusive conversation with aspiring space tourist (and NSYNC bassist) Lance Bass, speaking several times with the International Space Station, witnessing five human spaceflight launches on two continents, flying parabolic, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, " Why Am I Taller ?", is co-written with astronaut Dave Williams. Elizabeth holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, a Bachelor of Journalism from Canada's Carleton University and a Bachelor of History from Canada's Athabasca University. Elizabeth is also a post-secondary instructor in communications and science at several institutions since 2015; her experience includes developing and teaching an astronomy course at Canada's Algonquin College (with Indigenous content as well) to more than 1,000 students since 2020. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday. Mastodon: https://qoto.org/@howellspace

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Science News

50 years ago, the first probe to visit mercury launched.

Excerpt from the November 10, 1973 issue of Science News

Mariner 10 flew by Mercury three times from 1974 to 1975. The NASA spacecraft encountered a cratered, moonlike terrain as it mapped the planet’s surface (a photomosaic of the southern hemisphere shown).

JPL-Caltech/NASA

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By Christopher Crockett

November 8, 2023 at 11:39 am

Off to Mercury with a cold glance —  Science News ,  November 10, 1973

Mercury ho! Mariner 10 is on its way. Venus ho, too. Launched at 12:45 a.m. (EST) on Nov. 3, Mariner should pass within 3,330 miles of Venus on Feb. 5. It will then become the first spacecraft to use a technique … of letting the gravitational field of one planet bend its course around toward a second objective. That’s Mercury, of course, where it will arrive less than two months later.

Mariner 10 arrived on schedule, becoming the first probe to visit Mercury and map a portion of its cratered, moonlike terrain. The gravity assist that Mariner used to reach its destination is now a trusted way to get around the solar system ( SN: 7/12/15; SN: 7/5/18 ). NASA’s MESSENGER spacecraft used gravity assists from Mercury, Venus and Earth to reach an orbit around Mercury in 2011, where the probe mapped the rest of the planet’s surface, uncovered evidence of past volcanism and spotted signs of water ice and organic compounds ( SN: 11/29/11 ; SN: 3/22/12; SN: 11/30/12 ).

Today, the international BepiColombo mission is using gravitational assists from Mercury — following one from Earth and two from Venus — to steer itself into eventual orbit around the planet ( SN: 1/15/21 ). Beginning in 2025, BepiColombo will investigate Mercury’s innards and magnetic field.

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Mariner 10, a mission of firsts, used gravity to bend its way from Venus to Mercury

To the ancient Romans, Mercury was the messenger of the gods, his winged sandals adroitly whisking the maestro of luck and trickery to do his divine masters’ bidding. Small wonder that the nearest planet to the Sun was named in his honor: Crater-pocked Mercury whips around our parent star in 88 days at a mean distance of 36 million miles (58 million kilometers), two-thirds closer than Earth.

Brutalized by aeons of remorseless meteoroid bombardment, Mercury is a barren, broiling world of extremes. In its coal-dark sky, the Sun appears 11 times brighter, three times bigger, and many times hotter than here on Earth. Its 3:2 spin-orbit resonance and orbital eccentricity produced a Moon-like surface of mountains and plains, scarps and valleys, frozen to minus 170 degrees Celsius (minus 270 degrees Fahrenheit) at night then baked as high as 420 degrees Celsius (790 degrees Fahrenheit) in the mercurian daytime.

Fifty years ago, humanity gained its first up-close glimpse of this battered world when NASA’s Mariner 10 spacecraft made the first of three Mercury encounters. Its seven science instruments revealed heavily cratered highlands and rolling lowlands, the Caloris impact basin, and surprisingly (in view of Mercury’s geological deadness), an intrinsic magnetic field and hints of an iron-rich core.

But if Mariner 10’s mission was historic, so was the Boeing-built spacecraft itself, which for the first time used the gravity of one world (Venus) to reach another (Mercury) and in doing so visited two planets for the first time. It used extant hardware and technology to keep costs down, but engineers recognized that voyaging within 0.4 astronomical units (AU; 1 astronomical unit is equal to the average Earth-Sun distance of 93 million miles or 150 million km) of the Sun would impose 4.5 times greater solar radiation at Mercury than at Earth.

Get on the Mariner 10 bus

As such, Mariner 10’s octagonal spacecraft “bus” was guarded with thermal blankets of beta cloth (a combination of aluminized Kapton and glass-fiber sheets treated with Teflon) plus a sunshade and specialized louvers to regulate internal temperatures. Its two solar arrays, with a wingspan of 26 feet (7.6 meters), were rotatable through their long axes to minimize solar heating and keep them below 115 C (239 F). 

Mariner 10 bristled with cameras, an infrared radiometer to assess the thermal properties of Mercury’s surface, an ultraviolet spectrometer to sniff out a putative atmosphere, sensors to analyze interactions between the solar wind and cosmic radiation, two magnetometers on a 19-foot-long (5.8 m) hinged boom to seek evidence of an intrinsic magnetic field and a radio science toolkit to take mass and gravitational measurements. A 4.6-foot (1.4 m) high-gain antenna transmitted data at rates of 117.6 kilobits per second.

Previous Mariners flew in pairs to hedge against failure, but budget constraints had cost-capped Mariner 10 at $98 million. That allowed a spare spacecraft to be built in case of failure, but NASA decreed it could only fly if the fatal flaw was identified and resolved within two weeks. With Mariner 10 set to fly on Nov. 3, 1973, in the event of disaster the spare had to be ready to go no later than Nov. 21.

Meanwhile, Italian physicist Giuseppe Colombo suggested that Mariner 10’s trajectory following its March 1974 encounter of Mercury would permit a second flyby of the planet six months later. That layered greater complexity onto an already complex mission but carried the potential to greatly expand the scientific yield from an unknown world.

Mariner 10 launches in 1973

Mariner 10 launched atop an Atlas-Centaur rocket from Cape Canaveral’s Pad 36B at 12:45 a.m. EST on Nov. 3, 1973. Roaring aloft under 430,000 pounds (195,000 kilograms) of thrust, the Atlas booster shut down as planned four minutes into the flight, leaving the Centaur upper stage to perform two burns to firstly insert Mariner 10 into an Earth-parking orbit, then boost it into deep space.

It was a risky maneuver. Never before had two upper-stage burns been done on a U.S. planetary mission; an engine fault could spell the end for Mariner 10. With the exception of a drifting gyro, the Centaur performed admirably, pushing the 1,100-pound (500 kg) spacecraft out of Earth’s gravitational clutches and into interplanetary space at 25,458 mph (40,969 km/h). Ahead in 94 days lay its first planetary target: Venus.

But the cruise proved far from untroubled. Hours after launch, a cover failed to open on an electrostatic analyzer , nixing its use in an electron spectrometer experiment. Mariner 10’s star tracker repeatedly lost its lock on Canopus, locking its gaze instead onto stray flecks of paint. Multiple computer resets and high-gain antenna glitches turned a low-level headache for NASA engineers into a full-blown, three-month migraine.

Worse, short-circuiting heaters on the spacecraft’s cameras failed to activate, threatening permanent damage from the cold of deep space. Fortunately, the cameras’ normal mode of operation kept them warm enough to hover above critical temperature limits; they were left switched on during the cruise to Venus. Then, in an unexpected piece of good fortune, in January 1974 the heaters started working again.

On Feb. 5, Mariner 10 swept 3,584 miles (5,768 km) over Venus’ cloud-cloaked façade, acquiring 4,165 photographs and gathering data on atmospheric structures and near-surface temperatures. Near-ultraviolet measurements were taken of high-altitude, cirruslike chevron clouds.

But it proved a whistlestop tour. Venus’ gravity shaved the spacecraft’s velocity from 82,785 mph (133,230 km/h) to 72,215 mph (116,220 km/h), bending its flight path and reshaping its elliptical solar orbit to intersect Mercury. Seven weeks after passing Venus, and 146 days since departing Earth, the tiny planet emerged from the gloom.

Mariner 10 began photographing Mercury several days before closest approach, at first intermittently, then shooting a frame every 42 seconds by March 28. Next day, the spacecraft hurtled within 437 miles (703 km) of a world known for centuries as little more than a faint blob in telescope eyepieces, almost lost in the Sun’s glare. Heading outbound, it continued shuttering images until April 3.

Two thousand pictures streamed to expectant scientists back home. The Mercury I data uncovered a global magnetic field two orders of magnitude feebler than Earth’s own, arguably Mariner 10’s most unexpected find. And a vast impact basin crept teasingly into view, its yawning maw spanning over 830 miles (1,340 km), wider than Texas. Ringed by mile-high mountains, its location on the planet’s broiling, Sun-facing hemisphere earned it the apt moniker of Caloris Basin – Latin for “hot.”

Looping back around the Sun, Mariner 10 returned for its second visit, Mercury II, over the planet’s southern hemisphere on Sept. 21. Although the flyby distance of 29,870 miles (48,070 km) was wider, the viewing geometries were better. More data was also harvested from the spacecraft via improvements to NASA’s Deep Space Network (DSN), including the microwave antennas in Goldstone, California.

Six months later, on March 16, 1975, Mariner 10 encountered the planet a third time for Mercury III, passing over the north polar region at 203 miles (327 km), its closest yet. A failed tape recorder and restrictions in data-reception rates meant only the central quarter of 300 high-resolution photographs was received, but Mariner 10 managed to the image surface features as small as 328 feet (100 m) across.

Much of this remarkable extended mission was only possible thanks to engineers tripling the amount of hydrazine propellant for course correction maneuvers and extra nitrogen gas for its thrusters. But after Mercury III, fuel was low and the end was nigh. After traveling for 506 days and covering a billion miles (1.6 billion km), Mariner 10’s transmitter was shut down on March 24, 1975, and the mission concluded.

It had been a remarkable triumph, although the geometry of Mercury’s orbit during all three encounters meant the same side of the planet was sunlit each time, enabling Mariner 10 to map barely 40 to 45 percent of the surface. Nevertheless, the spacecraft’s 2,800 photographs revealed rugged highlands and smooth lowlands. Chains and clusters of craters embayed the highlands, and Mariner 10 data pointed to the existence of a tenuous exosphere of hydrogen and helium atoms captured from the solar wind, plus a bulk density consistent with a massive core, rich in iron and nickel.

Ground observations and NASA’s Messenger spacecraft have since mapped the planet in its entirety, hinting at water-ice in permanently shadowed polar craters. Europe’s BepiColombo mission will reach Mercury in December 2025 for its own extended orbital survey. And Mariner 10, which first shed light on this odd little world, now drifts silently in heliocentric space, unseen and untracked since contact went dead a half-century ago.

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Mariner 10: First mission to Mercury

Tim Wallace

By the time of humanity’s first close encounter with the Solar System’s first planet, when the Mariner 10 space probe passed 700 km from Mercury on 29 March 1974, missions to our planetary neighbours had been underway for more than a decade. Just over four dozen missions to Mars and Venus had been attempted by the Soviet Union and United States, with 17 successful.

The repeat visits to our two closest neighbours before the attempt on Mercury were due to the degree of difficulty involved: for a planet closer to the Sun, the greater the gravitational forces a spaceship must overcome to change its trajectory and speed. To send a spaceship to Mars (an average 78.3 million km away) is therefore easier than to Venus (an average 41.4 million km, but closer to the Sun). Sending a probe to Mercury (an average 91.7 million km from Earth, and just 57.9 million km from the Sun) requires more fuel than sending one to the outer limits of the Solar System.

So Mariner 10 was notable – and not just for being the first mission to Mercury. It was also the first mission to visit two planets, reaching its final destination by sling-shotting around Venus in the first use of the gravitational assist manoeuvre that is now a standard part of space navigation; and despite being the seventh probe to reach Venus, it provided the first detailed images of the planet. Another first was the use of an experimental ‘X-band’ high-frequency transmitter. 

The Mariner was built around an octagonal body 1.4 m across and 4.5 m deep, with eight separate electronics compartment protected by thermal blankets. It was equipped with just two solar panels, unlike the rest of the Mariner series that had four. There were two sets of reaction jets for stabilising the craft on three axes, and 29 kg of liquid fuel to power them. All up the craft weighed about 500 kg. 

Onboard instruments included a radiometer to detect infrared radiation; two spectrometers to detect ultraviolet radiation and emissions; plasma detectors to study solar wind; magnetometers to detect magnetic fields; telescopes to detect whether any magnetic fields had captured charged particles; and two 15 cm telescopes connected to a video imaging system. These were positioned on the side of the spacecraft intended to face away from the Sun, to protect the electronics from overheating. On the other side of of the craft an umbrella-like sunshade provided extra shielding from solar radiation. 

These photos of the the Earth and Moon were taken from 2.6 million km away. 

Shortly after its launch on 3 November 1973, Mariner 10 turned to take pictures of the Earth and Moon. The purpose was to calibrate its television cameras in preparation for its main mission. It was the first spacecraft capable of returning high-resolution digital color image data. Two images, taken at a distance of about 2.6 million km, are combined here to show their relative sizes.

Travelling at a speed of about 38,600 km/h, Mariner 10 reach its first mission objective three months later. On February 5, 1974 the spacecraft came within 5,631.5 km of the surface of Venus. 

During its time in close proximity to Venus, Mariner 10 took about 4000 images and carried out several important scientific observations despite severe technical problems that meant only a few of the thousands of commands for subsystems were executed by the probe’s onboard computer. 

While Venus appears featureless in normal light, due to its blanketing cloud, ultraviolet camera filters showed a much more dynamic atmosphere. The marbled look of the planet’s atmosphere indicates where more or less ultraviolet radiation is being absorbed. Based on observations from Earth, scientists had expected to see a blotchy surface, but the degree captured by Mariner 10 was a surprise to most, leading to much theorising about the causes. That speculation has continued to this day.

Venus’ gravity field first slowed the velocity of Mariner 10 to about 16,000 km/h and then slung it onto a new path toward Mercury. 

About five weeks later, on March 23, Mariner 10 began taking intermittent pictures of Mercury. At first, from at a distance of 5.3 million km, the images were little better than what could be observed through a telescope on Earth. But steadily they improved. By the time Mariner 10 was within 3.5 million km of Mercury the images being received back on Earth indicated how mottled the planet’s surface was, giving scientists an inkling of it being a crater-scarred landscape like the Moon.

On March 28, Mariner 10’s surveillance kicked into high gear, taking a picture every 42 seconds. On March 29 it reached its closest point to the planet, passing within 705 km of the surface. This flyby was over the planet’s dark side, so provided no usable photos, but the probe did return high-quality images before and after. It continued to take and send photos until April 3, when it was more than 3.5 million km from Mercury. All up it took and transmitted more than 2,000 photographs, which were received by tracking stations of the Deep Space Network in Goldstone, California; Tidbinbilla, Australia; and Madrid, Spain. 

From the observations Mariner sent home, scientists learned Mercury, while dense, has a magnetic field that is just 0.016% as strong as Earth’s.

The images of Mercury revealed a planet very much like our own Moon – indeed the planet is only 1.4 times the diameter of Earth’s satellite, though with a mass 4.6 times greater. Its surface is a barren scape of basins, craters, scarps, ridges and plains.

“Where the plains are absent, overlapping craters and basins form rugged terrain,” noted the technical report prepared by the Jet Propulsion Laboratory for NASA. “The plains materials have many of the same characteristics of the lunar maria and have been cratered to approximately the same degree. This twofold division of the morphology of Mercury is similar to that of the Moon.”

Mariner 10’s trajectory would bring it back into contact with Mercury twice more, looping around the Sun to intercept and complete close flybys in September 1974 and March 1975. On its third flyby it came within 330 km of the planet. Soon after it depleted all its fuel, and NASA turned off its transmitter on 24 March 1975.  

All told, Mariner 10 took about 7,000 photos of the Earth, Moon, Venus and Mercury.

It would be the last mission in NASA’s Mariner program (with two slated missions to visit Saturn and Jupiter becoming the first missions the Voyager program to explore the outer Solar System). It was almost 33 years before the next mission, MESSENGER, visited Mercury, arriving in January 2008.

Despite being the last of the Mariners, Mariner 10 remains a mission replete with firsts.

Originally published by Cosmos as Mariner 10: First mission to Mercury

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This Day In History : March 29

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U.S. space probe, Mariner, visits Mercury

The unmanned U.S. space probe Mariner 10 , launched by NASA in November 1973, becomes the first spacecraft to visit the planet Mercury, sending back close-up images of a celestial body usually obscured because of its proximity to the sun.

Mariner 10 had visited the planet Venus eight weeks before but only for the purpose of using Venus’ gravity to whip it toward the closest planet to the sun. In three flybys of Mercury between 1974 and 1975, the NASA spacecraft took detailed images of the planet and succeeded in mapping about 35 percent of its heavily cratered, moonlike surface.

Mercury is the smallest planet in the solar system and completes its solar orbit in only 88 earth days. Data sent back by Mariner 10 discounted a previously held theory that the planet does not spin on its axis; in fact, the planet has a very slow rotational period that stretches over 58 earth days. Mercury is a waterless, airless world that alternately bakes and freezes as it slowly rotates. Highly inhospitable, Mercury’s surface temperature varies from 800 degrees Fahrenheit when facing the sun to -279 degrees when facing away. The planet has no known satellites. 

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Mariner 10 was the first spacecraft to visit Planet Mercury. It was explored in three flybys by the Mariner 10 spacecraft in 1974 and 1975. It was launched by an Atlas-Centaur rocket in 3 November 1973.

Mariner 10 became the first and only spacecraft to reach Mercury in the twentieth century. The remotely controlled spacecraft flew to within 460 miles (740 kilometres) of Mercury on 29 March, 1974. It swept past the planet again on 24 September, 1974 and on 16 March, 1975. During those flights, the spacecraft photographed portions of the surface of Mercury. It also detected Mercury’s magnetic field.

Mariner 10 became the first spacecraft to study two planets. The probe photographed and made scientific measurements of Venus while travelling to Mercury. As the probe flew near Venus, the planet’s gravity pulled on the spacecraft, causing it to move faster. Thus, Mariner 10 reached Mercury in less time and by using less fuel than if it had flown directly from the Earth.

Mariner 10 was the seventh successful launch in the Mariner series and the first spacecraft to visit Mercury. It was also the first spacecraft to use the gravitational pull of one planet (Venus) to reach another (Mercury), and the first spacecraft mission to visit two planets.

The primary scientific objectives of the mission were to measure Mercury’s environment, atmosphere, surface, and body characteristics and to make similar investigations of Venus. Secondary objectives were to perform experiments in the interplanetary medium and to obtain experience with a dual-planet gravity-assist mission.

Did you know?

There were 10 Mariner missions from 1962 to 1973 which explored  Mars ,  Venus  and  Mercury .

NASA has explored Mercury with the MESSENGER Spacecraft.

In the future, ESA is planning to explore Mercury with  BepiColombo .

Mariner 10 Links:

• Nasa’s Mariner 10 Web Page :
• Mariner 10 Image Browser  (New)
• Mercury Mariner 10 Image Project

Any suggestions or comments, click on  Contact Info .

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The legacy of Mariner 10

Apr 1, 2016

42 years ago on March 29, NASA’s Mariner 10 mission became the first spacecraft to visit Mercury.

At the time of its launch, little was known about our planetary neighbors. Scientists were particularly interested in Mercury’s core and how Venus interacts with the solar wind. Despite mission challenges that included losing data transmissions, attitude control fuel problems and a flight data system that continually reset itself, Mariner 10 successfully reached Mercury after being the first spacecraft to use a gravity assist of one planet (Venus in this case) to reach another. The mission tested out new navigational techniques that would be used on future missions and also became a demonstration of how to adapt missions to changing circumstances on the fly- an important skill that NASA continues to use today.

Mariner 10 was the first two-planet exploration mission, providing valuable data on both Mercury and Venus. Pictures of Mercury’s surface showed craters and bare ground that looked similar to Earth’s moon and instruments detected a faint helium atmosphere in addition to a small magnetic field with a strength about one-sixtieth that of Earth’s. The mission also showed that the strength of Venus’ magnetic field was one-twentieth the strength of Earth’s, meaning it cannot not shield Venus to the same extent that Earth’s field does, nor do large clouds of particles congregate near the belts of Venus like they do near Earth.

Mariner 10’s most famous contribution to the public consciousness was a photograph of Venus which shows that a thick cloud layer with swirls and patches covers the planet, implying a very active atmosphere.

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Mariner 10, a mission of firsts, used gravity to bend its way from Venus to Mercury | Astronomy.com

Mariner 10 launched atop an Atlas-Centaur rocket from Cape Canaveral’s Pad 36B at 12:45 a.m. EST on Nov. 3, 1973. Roaring aloft below 430,000 kilos (195,000 kilograms) of thrust, the Atlas booster shut down as deliberate 4 minutes into the flight, leaving the Centaur higher stage to carry out two burns to firstly insert Mariner 10 into an Earth-parking orbit, then increase it into deep space.

It was a dangerous maneuver. By no means earlier than had two upper-stage burns been carried out on a U.S. planetary mission; an engine fault may spell the top for Mariner 10. Excluding a drifting gyro, the Centaur carried out admirably, pushing the 1,100-pound (500 kg) spacecraft out of Earth’s gravitational clutches and into interplanetary space at 25,458 mph (40,969 km/h). Forward in 94 days lay its first planetary goal: Venus.

However the cruise proved removed from untroubled. Hours after launch, a cover failed to open on an electrostatic analyzer , nixing its use in an electron spectrometer experiment. Mariner 10’s star tracker repeatedly misplaced its lock on Canopus, locking its gaze as an alternative onto stray flecks of paint. A number of laptop resets and high-gain antenna glitches turned a low-level headache for NASA engineers right into a full-blown, three-month migraine.

Worse, short-circuiting heaters on the spacecraft’s cameras didn’t activate, threatening everlasting harm from the chilly of deep space. Luckily, the cameras’ regular mode of operation saved them heat sufficient to hover above essential temperature limits; they have been left switched on through the cruise to Venus. Then, in an sudden piece of excellent fortune, in January 1974 the warmers began working once more.

On Feb. 5, Mariner 10 swept 3,584 miles (5,768 km) over Venus’ cloud-cloaked façade, buying 4,165 images and gathering knowledge on atmospheric constructions and near-surface temperatures. Close to-ultraviolet measurements have been taken of high-altitude, cirruslike chevron clouds.

But it surely proved a whistlestop tour. Venus’ gravity shaved the spacecraft’s velocity from 82,785 mph (133,230 km/h) to 72,215 mph (116,220 km/h), bending its flight path and reshaping its elliptical solar orbit to intersect Mercury. Seven weeks after passing Venus, and 146 days since departing Earth, the tiny planet emerged from the gloom.

Mariner 10 started photographing Mercury a number of days earlier than closest strategy, at first intermittently, then capturing a body each 42 seconds by March 28. Subsequent day, the spacecraft hurtled inside 437 miles (703 km) of a world identified for hundreds of years as little greater than a faint blob in telescope eyepieces, virtually misplaced within the Solar’s glare. Heading outbound, it continued shuttering pictures till April 3.

Two thousand footage streamed to expectant scientists again residence. The Mercury I knowledge uncovered a worldwide magnetic area two orders of magnitude feebler than Earth’s personal, arguably Mariner 10’s most sudden discover. And an enormous affect basin crept teasingly into view, its yawning maw spanning over 830 miles (1,340 km), wider than Texas. Ringed by mile-high mountains, its location on the planet’s broiling, Solar-facing hemisphere earned it the apt moniker of Caloris Basin – Latin for “sizzling.”

Looping again across the Solar, Mariner 10 returned for its second go to, Mercury II, over the planet’s southern hemisphere on Sept. 21. Though the flyby distance of 29,870 miles (48,070 km) was wider, the viewing geometries have been higher. Extra knowledge was additionally harvested from the spacecraft by way of enhancements to NASA’s Deep Area Community (DSN), together with the microwave antennas in Goldstone, California.

Six months later, on March 16, 1975, Mariner 10 encountered the planet a 3rd time for Mercury III, passing over the north polar area at 203 miles (327 km), its closest but. A failed tape recorder and restrictions in data-reception charges meant solely the central quarter of 300 high-resolution images was obtained, however Mariner 10 managed to the picture floor options as small as 328 ft (100 m) throughout.

A lot of this exceptional prolonged mission was solely potential due to engineers tripling the quantity of hydrazine propellant for course correction maneuvers and additional nitrogen gasoline for its thrusters. However after Mercury III, gas was low and the top was nigh. After touring for 506 days and masking a billion miles (1.6 billion km), Mariner 10’s transmitter was shut down on March 24, 1975, and the mission concluded.

It had been a exceptional triumph, though the geometry of Mercury’s orbit throughout all three encounters meant the identical facet of the planet was sunlit every time, enabling Mariner 10 to map barely 40 to 45 p.c of the floor. However, the spacecraft’s 2,800 images revealed rugged highlands and clean lowlands. Chains and clusters of craters embayed the highlands, and Mariner 10 knowledge pointed to the existence of a tenuous exosphere of hydrogen and helium atoms captured from the solar wind, plus a bulk density in step with an enormous core, wealthy in iron and nickel.

Floor observations and NASA’s Messenger spacecraft have since mapped the planet in its entirety, hinting at water-ice in completely shadowed polar craters. Europe’s BepiColombo mission will attain Mercury in December 2025 for its personal prolonged orbital survey. And Mariner 10, which first make clear this odd little world, now drifts silently in heliocentric space, unseen and untracked since contact went lifeless a half-century in the past.

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On Nov. 3, 1973, the Mariner Venus/Mercury 1973 spacecraft, also known as Mariner 10, was launched from NASA’s Kennedy Space Center, becoming the first spacecraft designed to use gravity assist. Three months after launch it flew by Venus, changed speed and trajectory, then crossed Mercury’s orbit in March 1974.

This photo identifies the spacecraft’s science instruments, which were used to study the atmospheric, surface and physical characteristics of Venus and Mercury. This was the sixth in the series of Mariner spacecraft that explored the inner planets beginning in 1962.

Image Credit: NASA/JPL