m−2). By about 350 BC, the ancient Greeks had realized the two stars were one. Mercury also presents difficulties to study by space probe. In 1800, Johann Schröter made observations of surface features, claiming to have observed 20-kilometre-high (12 mi) mountains. a Mercury is one of four inner planets in the Solar System, and has a rocky body like the Earth.It is the smallest planet in the Solar System, with a radius of 2,439.7 km (1,516.0 mi). It rules commerce and media. IAU Working Group and Task Group Members. Mercury Data. It is the closest planet to the sun . At both of these times Mercury's separation from the Sun ranges anywhere from 17.9° at perihelion to 27.8° at aphelion. [171] Mariner 10 provided the first close-up images of Mercury's surface, which immediately showed its heavily cratered nature, and revealed many other types of geological features, such as the giant scarps that were later ascribed to the effect of the planet shrinking slightly as its iron core cools. References: MESSENGER Mercury Dual Imaging System (MDIS) Experiment Data Record (EDR) Software Interface Specification (SIS) document, The Johns Hopkins University, APL, V2T, Jun. a mean distance from Sun 57,909,227 km (0.39 AU) eccentricity of orbit 0.2056 inclination of the semi-major axis, and Therefore, the spacecraft must make a large change in velocity (delta-v) to get to Mercury and then enter orbit, as compared to the delta-v required for other planetary missions. The detection of high amounts of water-related ions like O+, OH−, and H3O+ was a surprise. [82][83] Like that of Earth, Mercury's magnetic field is dipolar. Astronomers were reluctant to drop the synchronous rotation theory and proposed alternative mechanisms such as powerful heat-distributing winds to explain the observations. MESSENGER’s voyage to Mercury surpassed expectations and ended with its descent and impact onto the surface on April 30, 2015. With a radius of about 2,440 km (1,516 miles), Mercury is the smallest major planet, smaller even than Jupiter’s largest moon, Ganymede, or Saturn’s largest moon, Titan. Mercury's surface is more heterogeneous than either Mars 's or the Moon 's, both of which contain significant stretches of similar geology, such as maria and plateaus. While the suite of sensors are designed to study the rocky, atmosphere-free environment at Mercury, the flyby offered a unique opportunity to collect valuable science data at Venus. " Four Earth days after perihelion, the Sun's normal apparent motion resumes. Planetary Names: Mercury Home . Maximum temperature occurs when the Sun is at an angle of about 25 degrees past noon due to diurnal temperature lag, at 0.4 Mercury days and 0.8 Mercury years past sunrise. Earth – The only planet in our solar system with liquid water on the surface. MESSENGER found high proportions of calcium, helium, hydroxide, magnesium, oxygen, potassium, silicon and sodium. From the perspective of the warm poles, the Sun is already low on the horizon and about to set when it grows the brightest and performs its brief course reversal. 2 [4] The mission comprises two satellites launched together: the Mercury Planetary Orbiter (MPO) and Mio (Mercury Magnetospheric Orbiter, MMO). planets (planetary systems for planets with natural satellites) were taken from published val-ues derived from spacecraft tracking data. Some four and a half decades after NASA’s Mariner 10 spacecraft sped by Mercury, a group of planetary scientists is now talking about landing on … The planet’s rotation period of 58.6 Earth days with respect to the stars—i.e., the length of its sidereal day—causes the Sun to drift slowly westward in Mercury’s sky. [154] This phenomenon is known as synchronous rotation. Because of where the planets are on these orbital paths, and specifically the time it takes Mercury to orbit the sun, Mercury is the planet that is closest to Earth more often and has an average distance to Earth that is lower than the other 2 inner planets. In 1639, Giovanni Zupi used a telescope to discover that the planet had orbital phases similar to Venus and the Moon. About. Cambridge University Press. It is "new" at inferior conjunction and "full" at superior conjunction. 17, June 10, 1975. While the suite of sensors are designed to study the rocky, atmosphere-free environment at Mercury, the flyby offered a unique opportunity to collect valuable science data at Venus. [92] This is significantly smaller than that of Jupiter, which has the second smallest axial tilt of all planets at 3.1 degrees. The probe successfully entered an elliptical orbit around the planet on March 18, 2011. [175] At the first close approach, instruments detected a magnetic field, to the great surprise of planetary geologists—Mercury's rotation was expected to be much too slow to generate a significant dynamo effect. Because the planet is located deep in the Sun’s gravity field, a great deal of energy is needed to shape the trajectory of a spacecraft to get it from Earth’s orbit to Mercury’s in such a way that it can go into orbit around the planet or land on it. The radar studies revealed that the planet’s 58.6-day rotation period is not only different from its orbital period but also exactly two-thirds of it. This means that to an observer at Mercury's poles, the center of the Sun never rises more than 2.1 arcminutes above the horizon. The latest JPL ephemeris with fully consistent treatment of planetary and lunar laser ranging data is DE440 (Park et al., 2021). This contributes to the space weathering of the planet's surface. [172] Unfortunately, the same face of the planet was lit at each of Mariner 10's close approaches. [14] This exosphere is not stable—atoms are continuously lost and replenished from a variety of sources. An alternate method for viewing Mercury involves observing the planet during daylight hours when conditions are clear, ideally when it is at its greatest elongation. Planetary data for Mercury *Time required for the planet to return to the same position in the sky relative to the Sun as seen from Earth. The MPO design is optimised to meet the needs of the payload when the spacecraft is in its operational orbit. This small motion, about 9.5′ (0.16°) of arc per century, has been known for two centuries, and, in fact, all but about 7 percent of it—corresponding to 43″ (0.012°) of arc—could be explained by the theory of gravity proposed by Isaac Newton. Mercury is even smaller—albeit more massive—than the largest natural satellites in … In 2000, high-resolution lucky imaging observations were conducted by the Mount Wilson Observatory 1.5 meter Hale telescope. However, with noticeable eccentricity, like that of Mercury's orbit, the tidal force has a maximum at perihelion and therefore stabilizes resonances, like 3:2, enforcing that the planet points its axis of least inertia roughly at the Sun when passing through perihelion. [138], In ancient China, Mercury was known as "the Hour Star" (Chen-xing 辰星). During that time, the spacecraft orbit pericenter was always over the northern hemisphere. [70], The icy regions are estimated to contain about 1014–1015 kg of ice,[71] and may be covered by a layer of regolith that inhibits sublimation. 2009; Rivoldini and Van Hoolst 2013; Hauck II et al. These lines will then build up into a cool pattern over 40 earth years of orbital cycles. The Sun's total angular displacement during its apparent retrograde motion as seen from the surface of Mercury is ~1.23°, while the Sun's angular diameter when the apparent retrograde motion begins and ends is ~1.71°, increasing to ~1.73° at perihelion (midway through the retrograde motion). [87], Mercury has the most eccentric orbit of all the planets; its eccentricity is 0.21 with its distance from the Sun ranging from 46,000,000 to 70,000,000 km (29,000,000 to 43,000,000 mi). Measurements of changes in the probe's orbital velocity were expected to be used to infer details of the planet's interior structure. To land safely or enter a stable orbit the spacecraft would rely entirely on rocket motors. The magnetic-field strength at Mercury's equator is about 300 nT. Nearly two-thirds of Mercury’s mass is contained in its largely iron core, which extends from the planet’s centre to a radius of about 2,100 km (1,300 miles), or about 85 percent of the way to its surface. [104], The rare 3:2 resonant tidal locking is stabilized by the variance of the tidal force along Mercury's eccentric orbit, acting on a permanent dipole component of Mercury's mass distribution. CS1 maint: DOI inactive as of November 2020 (. MESSENGER data for scientific use is available from the Planetary Data System archive. Viewed from low latitudes and at the right times of year, the ecliptic intersects the horizon at a steep angle. It travels around the sun at a faster speed than any other planet. [153] In the 1880s, Giovanni Schiaparelli mapped the planet more accurately, and suggested that Mercury's rotational period was 88 days, the same as its orbital period due to tidal locking. [68] Water ice strongly reflects radar, and observations by the 70-meter Goldstone Solar System Radar and the VLA in the early 1990s revealed that there are patches of high radar reflection near the poles. , where Until Earth-based radar observations proved otherwise in the 1960s, astronomers had long believed that to be the case, which would follow if Mercury’s rotation were synchronous—that is, if its rotation period were the same as its 88-day revolution period. [162] Data from Mariner 10 subsequently confirmed this view. The effort to map the surface of Mercury was continued by Eugenios Antoniadi, who published a book in 1934 that included both maps and his own observations. He suggested, among possible explanations, that another planet (or perhaps instead a series of smaller 'corpuscules') might exist in an orbit even closer to the Sun than that of Mercury, to account for this perturbation. T [81] Many of the planet's surface features, particularly the albedo features, take their names from Antoniadi's map. For more information about USGS planetary science efforts, visit the USGS Astrogeology Science Center website. 2 The effect appears as a gyration, or precession, of Mercury’s orbit around the Sun. Mercury has an orbital speed of 48 km/s (30 mi/s), whereas Earth's orbital speed is 30 km/s (19 mi/s). Mercury can come as near as 82.2 gigametres (0.549 astronomical units; 51.1 million miles) to Earth, and that is slowly declining: The next approach to within 82.1 Gm (51.0 million miles) is in 2679, and to within 82.0 Gm (51.0 million miles) in 4487, but it will not be closer to Earth than 80 Gm (50 million miles) until 28,622. MESSENGER data used for DE430 and DE431 are from the first year in orbit about Mercury. Venus – Venus’ thick atmosphere makes it the hottest planet in our solar system. The way we organize, synthesize and transfer data also falls to Mercury, which governs our mobile devices, scheduling and transportation. {\displaystyle e} [123], The earliest known recorded observations of Mercury are from the Mul.Apin tablets. [156][157][158] Three years later, radar observations by Americans Gordon H. Pettengill and Rolf B. Dyce, using the 300-meter Arecibo radio telescope in Puerto Rico, showed conclusively that the planet's rotational period was about 59 days. Internal Structure: Mercury is one of four terrestrial planets in the Solar System, and is a rocky body like the Earth. It’s a little bigger than Earth’s Moon. Try to win a Planetary Society Venn Diagram tee and a signed copy of Emily Lakdawalla’s book, The Design and Engineering of Curiosity, by answering this question: What was the first human-made object to hit another world besides Earth? Orbital periods of the four inner rocky planets: Mercury: 88 days; Venus: 225 days; Earth:365 days; Mars: 687 days ( Mercury's thin atmosphere, or exosphere, is composed mostly of oxygen (O2), sodium (Na), hydrogen (H2), helium (He), and potassium (K). [f][130] Babylonian records of Mercury date back to the 1st millennium BC. Because of its nearness to the Sun—its average orbital distance is 58 million km (36 million miles)—it has the shortest year (a revolution period of 88 days) and receives the most intense solar radiation of all the planets. A Mercury-bound spacecraft launched from Earth must travel over 91 million kilometres (57 million miles) into the Sun's gravitational potential well.

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