The Mercury planet is the closest planet to our Sun and the smallest in size within the Solar System. Romans named this small and cratered planet after their Messenger God due to its lack of moons.

Mercury is the second densest planet after Earth. It boasts a dense metallic core measuring 2,200 to 2,400 miles (3,600 to 3800 km), making up approximately 75% of its total size.

Meanwhile, its outer layer only extends 500 to 600 kilometres (300 to 400 miles). Scientists have long been baffled by Mercury’s large inner core combined with a composition containing abundant volatile elements – something no other planet offers as an explanation.

Mercury was known to the Sumerians at least 5,000 years ago. A NASA MESSENGER mission site reports that Mercury was associated with Nabu, their god of writing.

Mercury earned two names when appearing as morning and evening stars; Greek astronomers understood that both names referred to one body. Around 500 B.C., Heraclitus correctly predicted that Mercury and Venus orbited Earth rather than the Sun.

How Hot is Mercury?

Mercury’s surface can reach an incredibly hot 840 degrees Fahrenheit due to its proximity to the Sun. Since this planet doesn’t have a lot of atmosphere, temperatures can drop to minus 170 degrees Celsius (minus 275 degrees F). This is the largest temperature swing in the solar system.

How Big is Mercury?

Mercury is one of the smallest planets in our solar system and slightly bigger than Earth’s Moon. Mercury is covered with numerous craters due to impact without an atmosphere to cushion impacts.

A 60-mile-wide (100 km wide) asteroid struck Mercury approximately 4 billion years ago with the force equivalent to 1 trillion one-megaton bombs, creating a massive impact crater estimated to cover an area larger than Texas – Caloris Basin being such a crater.

Another large impact may also have caused its odd spin – according to another 2011 study another large impact may have contributed to the planet’s odd spin.

Mercury Surfaces Characteristics

NASA’s MESSENGER satellite discovered water ice at Mercury’s north pole 2012. Due to Mercury being so close to the Sun, areas shaded from it remain permanently in shadow;

Unfortunately, MESSENGER couldn’t explore Mercury’s southern pole; comets, meteorites or even water vapour may have contributed to ice formation on both poles.

Structure and Surface

• Mercury is the smallest of all planets in our solar system.
• Mercury is a planet that’s on Earth. It is a small, rocky planet.
• Mercury does not have an atmosphere.

Time on Mercury

• Mercury’s day lasts 59 Earth Days.
• Mercury’s year lasts 88 days on Earth.

Mercury’s Neighbours

• Mercury has no moons.
• Mercury is the nearest planet to the Sun.
• Venus is Mercury’s nearest planet.

Quick History

• Mercury is known to have existed since antiquity because it is visible without the use of advanced telescopes.
• Mercury was visited by two spacecraft, Mariner 10 & MESSENGER.

Mercury continues its diminutive trajectory today, as evidenced by a 2016 report. Mercury comprises one continent plate sitting atop a cooling core; as its iron core solidifies and contracts, Mercury contracts further.

Crumpled surface regions were crumpled into hundreds-mile-high scarps with vertical walls reaching over one kilometre long; one such location, known as Mercury’s Great Valley, was so extensive it was larger than Arizona’s Grand Canyon!

According to a NASA press release by Tom Watters, Smithsonian Senior Scientist from the National Air and Space Museum, Washington D.C, Mercury is still a young planet, and as it cools and contracts, new fault lines are likely to form today.

A 2016 study of Mercury’s surface cliffs indicates that its earthquake activity may remain ongoing. Mercury has also experienced frequent volcanic activity throughout its history; yet another 2016 study suggested that its eruptions ended 3.5 billion years ago.

A 2016 study suggested that Mercury’s surfaces can be divided into two general groups. One comprises older material that melted under higher pressure near its core-mantle boundary; the second forms closer to Mercury’s surface.

Carbon was identified as being responsible for its dark colour in 2016 research; researchers believe it may even have originated as part of Mercury’s primordial crust rather than having cometary origins.

Mercury’s Magnetic Field

Mariner 10 made an unexpected discovery: Mercury had an astonishing magnetic field. Planets can only generate magnetic fields when their core is still hot enough for rapid spinning;

In theory, such conditions require having a core with liquid core material that remains liquid even while moving rapidly – however, Mercury rotates every 59 days and has only one-third of the mass of Earth, so its core should have already cooled considerably over time.

Christopher Russell, professor at the University of California Los Angeles, stated in a press release from UCL that they knew how Earth worked.

So, they presumed it would work similarly when Mercury emerged as another terrestrial rock planet with an iron core.

Mercury’s magnetic fields differ significantly from Earth’s due to its distinctive interior structure. MESSENGER observations revealed that Mercury’s northern magnetic field was approximately three times stronger than its southern one, suggesting a change from liquid into solid material at its outer boundary rather than the interior of Mercury’s core. Russell co-authored a mathematical model which suggests this theory.

Russell explained, “Like a snowstorm, iron is being precipitated through Mercury’s magnetic fields like snow. Our analysis demonstrates this through its study on Mercury’s magnetic field powering fluid which creates its magnetic field.”

Earth-based radar observation may explain Mercury’s magnetism, which shows its core is still liquid; however, solar wind could play a part in dampening its magnetic field.

Mercury’s magnetic field may only be one-tenth as strong as Earth’s, yet its activity remains highly dynamic. Mercury’s field is frequently touched by solar winds – charged particles streaming off its Sun – creating powerful magnetic tornadoes that directly channel hot, fast plasma to its surface.

Does Mercury Have An Atmosphere?

Mercury has a thin “exosphere” of atoms blown off its surface due to solar radiation, solar wind, and micrometeoroid impact. NASA says these particles quickly escape into space and form a trail of particles.

Mercury’s atmosphere is an “exosphere bound to the surface, which is essentially a vacuum.” According to NASA, it contains 42% oxygen and 29% sodium. It also contains 22% hydrogen.

Mercury Orbit

Mercury travels the fastest of any planet through space at 112,000 km/h (180,000 mph). Mercury’s orbit can bring it as close to the Sun as 29 million miles or 47 million kilometres or as far away as 43 million miles (70 million km). When Mercury was closest to us, one would experience a three times larger surface area.

Mercury orbits the Sun over 59 days. On its scorched surface, the Sun appears briefly to rise before setting and rising again before slowly heading westward. At sunset, its shadow briefly rises before quickly setting back down again as night falls.

Mercury crossed Earth’s orbit around the Sun in 2016, making for a rare astronomical event that may have revealed information about its atmosphere and helped NASA improve some of their instruments.

According to The New York Times, Mercury orbits around the Sun in just 364 days versus Earth’s 365, making Earth’s orbit of just 90 days possible.

Therefore, Mercury passes Earth three to four times yearly on its journey around the Sun, creating an optical illusion whereby Mercury appears to travel “backwards”.

When this occurs for three weeks, it is known as a retrograde movement; Mercury should not be mistakenly considered a star!

Missions on Mercury Planet by NASA

Here you see 3 successful mission on Mercury planet such as:

Mariner 10?

Mariner 10 was the inaugural spacecraft sent to Mercury, and its mission explored two planets (Mercury and Venus). Furthermore, it returned to its initial destination for another look before using a gravity assist to change its flight path.

Nation	United States of America (USA)
Objective(s)	Mercury Flyby, Venus Flyby
Spacecraft	Mariner-73J / Mariner-J
Spacecraft Mass	1,100 pounds (502.9 kilograms)
Spacecraft Power	Solar
Mission Design and Management	NASA / JPL
Launch Vehicle	Atlas Centaur (AC-34 / Atlas 3D no. 5014D / Centaur D-1A)
Launch Date and Time	Nov. 3, 1973 / 05:45:00 UT
Launch Site	Cape Canaveral, Fla. / Launch Complex 36B
Scientific Instruments	1. Two Telescopes/Cameras2. Infrared Radiometer3. Ultraviolet Airglow Spectrometer4. Ultraviolet Occultation Spectrometer5. Magnetometer6. Charged Particle Telescope7. Plasma Analyzer

Firsts

• First spacecraft to study Mercury
• First spacecraft that uses the gravity of a planet (in this instance, Venus) to reach a second
• The first spacecraft to send back data on a comet over a long period
• First mission to visit two planets at once (Mercury & Venus).
• The first spacecraft used gravity assistance to change its flight trajectory
• First spacecraft to return after initial contact
• First spacecraft to use solar wind for orientation during flight

Results

Mariner 10 was the inaugural mission to explore Mercury and Venus simultaneously, using gravity assistance to alter its flight path, returning to its initial target after encounters, and using solar wind to keep itself on course during flight.

Mariner 10 was designed to explore Mercury’s surface, physical characteristics and atmosphere. Shortly after leaving Earth’s orbit, Mariner 10 captured stunning photographs of Earth and the Moon before heading toward Venus as its initial target destination.

Mariner 10 experienced technical issues during its journey, such as problems with its high-gain radio antenna and attitude control system.

After much effort to regain contact, data was transmitted back in January 1974 from Comet C/1973E1 Kohoutek for analysis – marking the first time that any spacecraft had successfully returned data on an object within such a long period.

Mariner 10 made midcourse corrections on November 13, 1973, and January 21, 74, before approaching Venus for its gravity-assist manoeuvre and subsequent manoeuvre towards Mercury.

Mariner 10 began returning images on February 5, 1974. This image showed for the first time the terminator between day and night on Venus as an extremely thin bright line;

Furthermore, it collected scientific data and took 4,165 images during its flyby distance of 3,584 miles (5 768 kilometres), which took place at 1701 UTC on February 5, 1974.

Mariner 10 was now propelled forward by Venusian gravity and headed toward Mercury – eventually arriving after another course correction on March 16, 1974, and taking photos of Mercury’s surface, similar to that of the Moon with craters and ridges.

Magnetometer readings revealed a weak field. Radiometer measurements indicated nighttime temperatures at 297 Fahrenheit (182 Celsius). Daytime maximum temperatures reached 369 Fahrenheit.

At 20:47 on March 29 at a distance of 703 kilometres (437 miles), Earth came closest to Jupiter at an encounter distance of 703 kilometres (437 miles).

A vehicle occultation test conducted while crossing behind its nightside revealed no evidence of atmosphere or ionosphere on Mars.

Mariner 10 left Mercury behind and looped around the Sun, returning to its initial target. To assist this journey, course corrections were implemented on May 9, May 10, and July 2, 1974, before passing near Mercury again at approximately 29,869 miles (48.069 kilometres) distance on September 21, 1974, at 20:59 UTC with imagery from its southern polar region captured at that time.

Solar pressure applied directly to its solar panels controlled its attitude, allowing accurate spacecraft navigation using a high-gain antenna.

Mariner 10 then accelerated away from Mercury before its third and final encounter, made possible through three manoeuvres on October 30, 1974, and March 7, 1975, to avoid impact with Mercury.

At 22:39 UTC on March 16, 1975, Mariner’s closest approach was approximately 200 miles (327 km).

Due to a lack of recording devices and slow data transmission rates, only the middle quarter of every 300 high-resolution pictures was received at this meeting.

On March 24, 1975, at 12:21 UTC, contact with the spacecraft had been lost as its gas supply for attitude control had run dry.

Mariner 10 captured over 2,700 images of Mercury during its three flybys, covering nearly half its land surface and providing details as small as 100 meters (328 feet).

Caloris basin stood out as perhaps its most striking feature with concentric rings and ridges stretching 1,550 miles (2,500 kilometres).

This was the first robotic probe to visit Mercury for over three decades.

Messenger

NASA’s MESSENGER orbited Mercury in an elliptical orbit for over four years. The mission’s accomplishments included determining Mercury’s surface, revealing its geological past, discovering details about its magnetic field, and verifying its polar deposits dominated by water-ice. The mission ended as MESSENGER slammed against Mercury’s surface.

Nation	United States of America (USA)
Objective(s)	Mercury Orbit
Spacecraft	MESSENGER
Spacecraft Mass	2,443 pounds (1,107.9 kilograms)
Mission Design and Management	NASA / APL
Launch Vehicle	Delta 7925H (no. D307)
Launch Date and Time	Aug. 3, 2004 / 06:15:57 UT
Launch Site	Cape Canaveral, Florida / SLC-17B
Scientific Instruments	Mercury Dual Imaging System (MDIS)Gamma-ray Spectrometer (GRS)Neutron Spectrometer (NS)X-ray Spectrometer (XRS)Magnetometer (MAG)Mercury Laser Altimeter (MLA)Mercury Atmospheric and Surface Composition Spectrometer (MASCS)Energetic Particle and Plasma Spectrometer (EPPS)Radio Science Experiment (RS)

Dates to Remember

August 3, 2004, Launch

March 11, 2011: MESSENGER has finally orbited Mercury seven years after its launch.

April 30, 2015: MESSENGER MESSENGER plunged into Mercury at the end of its mission

In-Depth:

MESSENGER was the seventh Discovery class mission and the first spacecraft to orbit Mercury. Its primary goal was to study its magnetic field, chemical composition, and geology – more than 30 years since Mariner 10’s successful mission.

On August 3, 2004, at 06:15.57 UTC, MESSENGER was launched into an Earth parking orbit and placed into an escape trajectory to heliocentric orbit with an orbital distance of 0.92x 1AU and 6.4% inclined toward the ecliptic. A PAM-D solid engine fired shortly afterwards to propel MESSENGER onward.

This mosaic created with the Wide Angle Camera (WAC) aboard MESSENGER highlights subtle colours on Mercury’s s surface. NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie

Mercury undertook several gravity-assisted manoeuvres during its six-and-a-half-year journey through the inner solar systems, including flybys of Earth (August 2, 2005) and Venus (October 24, 2006, and June 5, 2007) before coming close to Mercury several times (January 14, 2008, October 6, 2008, and September 29, 2009.).

Gravity-assist manoeuvres allowed MESSENGER to overcome the massive acceleration caused by its journey towards the Sun. Furthermore, flybys helped conserve propellant and slow the MESSENGER’s speed relative to Mercury (though they extended its journey).

Flybys of Earth allowed mission controllers to calibrate instruments onboard the spacecraft and capture spectacular images of Earth-Moon systems.

MESSENGER transmitted impressive data during its second Venusian Flyby, at only 210 miles (338 km). Images in visible and near-infrared wavelengths captured Venus’s upper atmosphere.

At the same time, ESA’s Venus Express Mission coordinated investigations, including particle and field characteristics studies of Venus.

The three Mercury flybys slowed MESSENGER further, and during its final encounter in September 2009 MESSENGER went into safe mode, meaning it did not collect any data on Mercury; seven hours later it was back up and running normally again.

MESSENGER entered its orbit around Mercury on March 18, 2011, at 00.45 UTC nearly seven years after launch. It began formal data collection on April 4, 2011.

The orbit of the vehicle was highly elliptical. It measured approximately 9,300 km by 200 km (about 5,800 by 12 miles) and had a period of 12 hours.

On February 18, 2011, from MESSENGER came an amazing image showing all planets except Uranus, Neptune and Pluto; an accurate visual equivalent to what Voyager 1 captured back in February 1990.

This spacecraft completed its year-long primary mission on Mercury and captured nearly 100,000 images.

Initial discoveries included:

• Discovering high concentrations of magnesium and calcium on Mercury’s nightside.
• Noting an offset northward of Mercury’s magnetism from its centre.
• Discovering large quantities of water within Mercury’s exosphere and uncovering evidence for past volcanic activity.

NASA announced in November 2011 that MESSENGER would receive an extended mission to monitor solar maximum in 2012. This period ran from March 18, 2012 – March 17, 2013.

On April 20, 2012, three engine firings took place to shorten MESSENGER’s orbit to 8 hours, and she captured her 100,000th photo during this period (early May 2012).

Her imaging instrument had completed global mapping of high-resolution colour and monochrome data covering Earth.

Mercury’s rotational tilt is nearly zero, making it possible to find water ice even in places never exposed to sunlight. The mission has been extended until March 2015 for another extension.

On February 6, 2014, NASA announced that MESSENGER had successfully taken its 200,000th photo orbitally, surpassing initial expectations of 1,000 images.

MESSENGER was successfully extended during its second extension, and two comets were photographed: Comet 2P/Encke (also known by its other name, Comet ISON) and Comet C/2012 S1

Beginning in the summer of 2014, controllers initiated a plan to move MESSENGER into low orbit to facilitate a new program.

On September 12, 2014 – exactly ten years after launch – the spacecraft’s orbit was reduced to only 15.5 miles (25 km).

Mission controllers carried out at least two orbital manoeuvres (September 12 and October 24) to increase the spacecraft’s orbit to continue its most recent extended mission.

On Christmas Day 2014, it became evident that MESSENGER would run out of fuel by late March 2015. Mission controllers performed one last manoeuvre on January 21, 2015, which raised its orbit enough for science activities to continue through early spring.

NASA announced on April 16, 2015, that its spacecraft, Mercury Odyssey, would crash into Mercury by April 30, 2015, once its fuel ran out.

On April 30, 2015, at 19:26 UTC, MESSENGER successfully collided with Mercury at approximately 8,750 miles per hour (14,080 km per hour), creating a new crater.

Impact coordinates likely lay near 54.4 degrees north longitude and 149.9 west latitude – near Janacek Crater in Suisei Planitia.

BepiColombo

BepiColombo is an international mission of two spacecraft that orbit Mercury and study it from unique perspectives. The European Space Agency provided one orbiter. The Japan Aerospace Exploration Agency supplied the second orbiter.

• BepiColombo was launched in October 2018 and is expected to orbit Mercury by 2025.
• ESA will use the Mercury Planetary Orbiter to study the surface and interior of Mercury.
• Mercury Magnetospheric Orbiter will be used to study the magnetic field of Mercury.
• The ESA and Japan are launching their first Mercury missions. Mercury has only been visited by two other spacecraft: NASA’s Mariner 10 (MESSENGER) and NASA’s Mariner 10.

Nation	Europe and Japan
Objective(s)	Mercury Orbit
Spacecraft	BepiColombo
Spacecraft Mass	9,040 pounds (4,100 kilograms)
Mission Design and Management	ESA and JAXA
Launch Vehicle	Ariane 5
Launch Date and Time	Oct. 20, 2018 | 01:45:28 UT
Launch Site	Guiana Space Centre, Kourou, French Guiana
Scientific Instruments	Mercury Planetary Orbiter (MPO): 2,540 pounds (1,150 kilograms)1. BELA–BepiColombo Laser Altimeter2. ISA–Italian Spring Accelerometer3. MPO-MAG–Magnetic Field Investigation4. MERTIS–Mercury Radiometer and Thermal Imaging Spectrometer5. MGNS–Mercury Gamma-Ray and Neutron Spectrometer6. MIXS–Mercury Imaging X-ray Spectrometer7. MORE–Mercury Orbiter Radio Science Experiment8. PHEBUS–Probing of Hermean Exosphere by Ultraviolet Spectroscopy9. SERENA–Search for Exosphere Refilling and Emitted Neutral Abundances (neutral and ionised particle analyzer)10. SIMBIO-SYS–Spectrometers and Imagers for MPO BepiColombo Integrated Observatory11. SIXS–Solar Intensity X-ray and Particle Spectrometer Mercury Magnetospheric Orbiter (MMO): 606 pounds (275 kilograms):1. MMO-MGF–Mercury Magnetometer2. MPPE–Mercury Plasma Particle Experiment3. PWI–Mercury Plasma Wave Instrument4. MSASI–Mercury Sodium Atmospheric Spectral Imager5. MDM–Mercury Dust Monitor

Key Dates

Oct. 20, 2018 | 01:45:28 UT: Launch

April 13, 2020: Earth flyby

Oct. 16, 2020: Venus flyby

Aug. 11, 2020: Venus Flyby

October 1, 2021: First Mercury flyby

June 23, 2022: Mercury flyby

June 20, 2023: Mercury flyby

September 5, 2024: Mercury flyby

December 2, 2024: Mercury flyby

January 9, 2025: Mercury flyby

December 5, 2025: Mercury orbital insertion

Firsts

• The Mercury mission is the first ESA mission.
• Mercury’s first JAXA mission
• The first mission to Mercury consisted of two orbiters.

BepiColombo: In Depth

BepiColombo, a joint European and Japanese mission to Mercury, seeks to study its composition, geophysics, atmosphere, magnetosphere and history.

The European Space Agency and Japan Aerospace Exploration Agency share orbiters on one spacecraft. ESA built the Mercury Magnetospheric Orbiter, while JAXA provided the Mercury Planetary Orbiter.

MPO will explore Mercury’s surface and composition from within. At the same time, MIO will look at its magnetosphere – the space surrounding Mercury that contains its magnetic field.

BepiColombo first flew past Mercury for the first time on October 1, 2021. It sent back images and will use several more flybys of planets to guide it into orbit around Mercury by December 2025.

BepiColombo will separate from its transfer module shortly before entering orbit and allow Mercury’s gravity to capture both orbiters together, leaving only their respective gravitational pull as their only anchors.

The orbiters should operate for approximately one year. BepiColombo was only the third spacecraft ever to visit Mercury after NASA’s Mariner 10 flew by three times between 1974 and 1975, providing images of Mercury.

NASA’s MESSENGER spacecraft orbited Mercury from August 3, 2004, until April 30, 2015, for over four years, studying its surface, geology, magnetic field, and polar deposits and confirming their water-ice nature.

Unfortunately, MESSENGER ran out of fuel during its journey and crashed to its fateful fate upon the planet’s surface.

BepiColombo was named in honour of Professor Giuseppe (Bepi) Colombo, an Italian mathematician, engineer, and professor at the University of Padua who first noticed Mercury rotating three times every two revolutions around the Sun due to an unknown resonance mechanism.

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