Instruct: Given a question, retrieve relevant passages that can help answer the question.
Query: How many days is the orbit of Mars?
Mars orbits the Sun in 687 days, spending about 57.25 days in each sign of the zodiac. It is also the first planet that orbits outside of Earth's orbit, making it the first planet that does not set along with the Sun. Mars has two permanent polar ice caps. During a pole's winter, it lies in continuous darkness, chilling the surface and causing the deposition of 25–30% of the atmosphere into slabs of CO ice (dry ice).
Mars 3 was an unmanned space probe of the Soviet Mars program which spanned the years between 1960 and 1973. Mars 3 was launched May 28, 1971, nine days after its twin spacecraft Mars 2. The probes were identical robotic spacecraft launched by Proton-K rockets with a Blok D upper stage, each consisting of an orbiter and an attached lander. After the Mars 2 lander crashed on the martian surface, Mars 3 lander became the first spacecraft to attain soft landing on Mars on 2 December 1971. It failed shortly after landing.The type of Orbiter was the Variant M-71 of the Bus/Obiter 4M-V. The primary purpose of the orbiter was to study the topography of the surface; analyze its soil composition; measure various properties of the atmosphere; monitor "solar radiation, the solar wind, and the interplanetary and martian magnetic fields". In addition, it served as a "communications relay to send signals from the lander to Earth".
Viking 1 was the first of two spacecraft (along with "Viking 2") sent to Mars as part of NASA's Viking program. On July 20, 1976, it became the second spacecraft to soft-land on Mars, and the first soft lander to successfully perform its mission. (The first spacecraft to soft-land on Mars was the Soviet Union's Mars 3 on December 2, 1971, which stopped transmitting after 14.5 seconds.) "Viking 1" held the record for the longest Mars surface mission of days (over 6¼ years) or Martian solar days, until that record was broken by "Opportunity" on May 19, 2010.
Perhaps inspired by Kepler (and quoting Kepler's third law of planetary motion), Jonathan Swift's satire "Gulliver's Travels" (1726) refers to two moons in Part 3, Chapter 3 (the "Voyage to Laputa"), in which Laputa's astronomers are described as having discovered two satellites of Mars orbiting at distances of 3 and 5 Martian diameters with periods of 10 and 21.5 hours. Phobos and Deimos (both found in 1877, more than a century after Swift's novel) have actual orbital distances of 1.4 and 3.5 Martian diameters, and their respective orbital periods are 7.66 and 30.35 hours. In the 20th century, V. G. Perminov, a spacecraft designer of early Soviet Mars and Venus spacecraft, speculated Swift found and deciphered records that Martians left on Earth. However, the view of most astronomers is that Swift was simply employing a common argument of the time, that as the inner planets Venus and Mercury had no satellites, Earth had one and Jupiter had four (known at the time), that Mars by analogy must have two. Furthermore, as they had not yet been discovered, it was reasoned that they must be small and close to Mars. This would lead Swift to making a roughly accurate estimate of their orbital distances and revolution periods. In addition Swift could have been helped in his calculations by his friend, the mathematician John Arbuthnot. 
Voltaire's 1752 short story "Micromégas", about an alien visitor to Earth, also refers to two moons of Mars. Voltaire was presumably influenced by Swift. In recognition of these 'predictions', two craters on Deimos are named Swift and Voltaire, while on Phobos there is one named regio, "Laputa Regio", and one named planitia, "Lagado Planitia", both of which are named after places in "Gulliver's Travels" (the fictional Laputa, a flying island, and Lagado, imaginary capital of the fictional nation Balnibarbi). Many of the craters on Phobos are also named after characters in "Gulliver's Travels".
Several planets or dwarf planets in the Solar System (such as Neptune and Pluto) have orbital periods that are in resonance with each other or with smaller bodies (this is also common in satellite systems). All except Mercury and Venus have natural satellites, often called "moons". Earth has one, Mars has two, and the giant planets have numerous moons in complex planetary-type systems. Many moons of the giant planets have features similar to those on the terrestrial planets and dwarf planets, and some have been studied as possible abodes of life (especially Europa).
Gravity on Mars is only about 38% as strong as it is on Earth, and the long-term effects of such reduced gravity are unknown. Astronauts who are weightless for long periods of time lose significant amounts of bone and muscle mass. It is unclear if the gravity on Mars is strong enough to avoid or minimize these health problems. The Mars Gravity Biosatellite was meant to provide data on how mammalian health is affected by long-term exposure to lower levels of gravity, focusing on bone loss, changes in bone structure, muscle atrophy, and changes in the inner ear. The results from the five-week mission experiment would have been compared against a variety of Earth-based controls, including vivarium, hindlimb suspension, partial weight suspension, flight habitat effects, and short-radius centrifuge testing.
Historically, an association between the color of blood and rust occurs in the association of the planet Mars, with the Roman god of war, since the planet is an orange-red, which reminded the ancients of blood. Although the color of the planet is due to iron compounds in combination with oxygen in the Martian soil, it is a common misconception that the iron in hemoglobin and its oxides gives blood its red color. The color is actually due to the porphyrin moiety of hemoglobin to which the iron is bound, not the iron itself, although the ligation and redox state of the iron can influence the pi to pi* or n to pi* electronic transitions of the porphyrin and hence its optical characteristics.
The USSR intended to have the first artificial satellite of Mars beating the planned American Mariner 8 and Mariner 9 Mars orbiters. In May 1971, one day after Mariner 8 malfunctioned at launch and failed to reach orbit, Cosmos 419 (Mars 1971C), a heavy probe of the Soviet Mars program M-71, also failed to launch. This spacecraft was designed as an orbiter only, while the next two probes of project M-71, Mars 2 and Mars 3, were multipurpose combinations of an orbiter and a lander with small skis-walking rovers that would be the first planet rovers outside the Moon. They were successfully launched in mid-May 1971 and reached Mars about seven months later. On November 27, 1971 the lander of Mars 2 crash-landed due to an on-board computer malfunction and became the first man-made object to reach the surface of Mars. On 2 December 1971, the Mars 3 lander became the first spacecraft to achieve a soft landing, but its transmission was interrupted after 14.5 seconds.
Mars 2020 is a Mars rover mission by NASA's Mars Exploration Program with a planned launch in July or August 2020. It will investigate an astrobiologically relevant ancient environment on Mars, investigate its surface geological processes and history, including the assessment of its past habitability, the possibility of past life on Mars, and the potential for preservation of biosignatures within accessible geological materials. It will cache sample containers along its route for a potential future Mars sample-return mission.
Fictional representations of Mars have been popular for over a century. Interest in Mars has been stimulated by the planet's dramatic red color, by early scientific speculations that its surface conditions might be capable of supporting life, and by the possibility that Mars could be colonized by humans in the future. Almost as popular as stories about Mars are stories about Martians engaging in activity (frequently invasions) away from their home planet.
The orbiter was initially proposed to be launched in September 2022 to link ground controllers with rovers and landers and extend mapping capabilities expected to be lost when the "Mars Reconnaissance Orbiter" and "2001 Mars Odyssey" stop functioning, but officials elected to focus on flying a sample-return mission first and incorporate a Mars telecom orbiter in that mission architecture, now envisioned for the late 2020s.
The moons of Mars may have started with a huge collision with a protoplanet one third the mass of Mars that formed a ring around Mars. The inner part of the ring formed a large moon. Gravitational interactions between this moon and the outer ring formed Phobos and Deimos. Later, the large moon crashed into Mars, but the two small moons remained in orbit. This theory agrees with the fine-grained surface of the moons and their high porosity. The outer disk would create fine-grained material.
While many Martian probes provided images and other data about Phobos and Deimos, only few were dedicated to these satellites and intended to perform a flyby or landing on the surface.
Ganymede (Jupiter III) is the largest and most massive moon of Jupiter and in the Solar System. The ninth largest object in the Solar System, it is the largest without a substantial atmosphere. It has a diameter of and is 8% larger than the planet Mercury, although only 45% as massive. Possessing a metallic core, it has the lowest moment of inertia factor of any solid body in the Solar System and is the only moon known to have a magnetic field. Outward from Jupiter, it is the seventh satellite and the third of the Galilean moons, the first group of objects discovered orbiting another planet. Ganymede orbits Jupiter in roughly seven days and is in a 1:2:4 orbital resonance with the moons Europa and Io, respectively.
Spirit, also known as MER-A (Mars Exploration Rover – A) or MER-2, is a robotic rover on Mars, active from 2004 to 2010. It was one of two rovers of NASA's ongoing Mars Exploration Rover Mission. It landed successfully on Mars at 04:35 Ground UTC on January 4, 2004, three weeks before its twin, "Opportunity" (MER-B), which landed on the other side of the planet. Its name was chosen through a NASA-sponsored student essay competition. The rover became stuck in late 2009, and its last communication with Earth was sent on March 22, 2010.
The path of the Sun in the local sky over the course of a local day during Uranus's and its major moons' summer solstice is quite different from that seen on most other Solar System worlds. The major moons have almost exactly the same rotational axial tilt as Uranus (their axes are parallel to that of Uranus). The Sun would appear to follow a circular path around Uranus's celestial pole in the sky, at the closest about 7 degrees from it. Near the equator, it would be seen nearly due north or due south (depending on the season). At latitudes higher than 7°, the Sun would trace a circular path about 15 degrees in diameter in the sky, and never set.
There have been four successful robotically operated Mars rovers. The Jet Propulsion Laboratory managed the "Sojourner" rover, the "Opportunity" rover, "Spirit" rover, and, now the "Curiosity" rover. On January 24, 2016 NASA reported that current studies on Mars by the "Curiosity" and "Opportunity" rovers would be searching for evidence of ancient life, including a biosphere based on autotrophic, chemotrophic or chemolithoautotrophic microorganisms, as well as ancient water, including fluvio-lacustrine environments (plains related to ancient rivers or lakes) that may have been habitable. The search for evidence of habitability, taphonomy (related to fossils), and organic carbon on Mars is now a primary NASA objective. Since June 2018, the "Opportunity" rover has been out of contact after going into hibernation mode in a dust storm. NASA has stated they are unsure if they will ever be able to regain contact.
Opportunity began the year at the edge of Endeavour Crater's Cape York, and the total distance travelled since landing on Mars was . After completing work at Matijevic Hill the "Opportunity" rover headed south to the rim of Endeavour Crater. Next, the rover headed south across a gap in the rim to a place the researchers called Botany Bay, then up onto the next rim segment to the south. There are two hills to the south of it, one called Solander Point and farther south is Cape Tribulation. The current aim is for "Opportunity" to reach Solander Point before winter reaches the Martian southern hemisphere as the area has ground tilted to the north allowing the rover to stay active during the winter months. In addition Solander Point has a large geological stack for Opportunity to explore.
In April 2013, the rover passed through a three-week-long solar conjunction, when communication with Earth was blocked because of the Sun. The rover arm was positioned on a rock during that time so the APXS could collect data.
NASA's "Mars Pathfinder" spacecraft, launched one month after Global Surveyor, landed on July 4, 1997. Its landing site was an ancient flood plain in Mars' northern hemisphere called Ares Vallis, which is among the rockiest parts of Mars. It carried a tiny remote-controlled rover called Sojourner, which was the first acting Mars rover that traveled a few meters around the landing site, exploring the conditions and sampling rocks around it. Newspapers around the world carried images of the lander dispatching the rover to explore the surface of Mars in a way never achieved before.
Among the remaining irregular moons, Sao and Laomedeia follow prograde orbits, whereas Halimede, Psamathe and Neso follow retrograde orbits. Given the similarity of their orbits, it was suggested that Neso and Psamathe could have a common origin in the break-up of a larger moon. Psamathe and Neso have the largest orbits of any natural satellites discovered in the Solar system to date. They take 25 years to orbit Neptune at an average of 125 times the distance between Earth and the Moon. Neptune has the largest Hill sphere in the Solar System, owing primarily to its large distance from the Sun; this allows it to retain control of such distant moons. Nevertheless, Jupiter's S/2003 J 2 orbits at the greatest percentage of the primary's Hill radius of all the moons in the Solar System on average, and the Jovian moons in the Carme and Pasiphae groups orbit at a greater percentage of their primary's Hill radius than Psamathe and Neso.
The mission will seek signs of habitable conditions on Mars in the ancient past, and will also search for evidence —or biosignatures— of past microbial life. The rover is planned for launch in 2020 on an Atlas V-541, and the Jet Propulsion Laboratory will manage the mission. The mission is part of NASA's Mars Exploration Program.
Many places on Mars show channels of different sizes. Many of these channels probably carried water, at least for a time. One study that used HiRISE pictures found over 17,000 km of ancient river valleys in Arabia Terra. Many ancient river valleys have been determined to be relatively recent, according to research published in 2016 in the Journal of Geophysical Research: Planets. These valleys carried water into lake basins. One lake, nicknamed "Heart Lake," had a volume similar to Lake Ontario. The climate of Mars may have been such in the past that water ran on its surface. It has been known for some time that Mars undergoes many large changes in its tilt or obliquity because its two small moons lack the gravity to stabilize it, as our moon stabilizes Earth; at times the tilt has even been greater than 80 degrees
The Mars Orbiter Mission probe lifted-off from the First Launch Pad at Satish Dhawan Space Centre (Sriharikota Range SHAR), Andhra Pradesh, using a Polar Satellite Launch Vehicle (PSLV) rocket C25 at 09:08 UTC on 5 November 2013. The launch window was approximately 20 days long and started on 28 October 2013. The MOM probe spent about a month in Earth orbit, where it made a series of seven apogee-raising orbital manoeuvres before trans-Mars injection on 30 November 2013 (UTC). After a 298-day transit to Mars, it was inserted into Mars orbit on 24 September 2014.
's orbit is very eccentric, with an aphelion beyond the orbit of Mars and a perihelion inside the orbit of Mercury. It has an orbital period of 360.29 days (0.99 years) and makes close approaches to Earth. But makes closer approaches to other inner planets, especially Mars. Its closest approach to a planet between 1950–2200 was to Mars, as it passed from Mars on 18 March 1964, and will pass from Mars on 12 October 2065.
"The Mars Project" is a technical specification for a manned mission to Mars that von Braun wrote in 1948, with a provisional launch date of 1965. He envisioned an "enormous scientific expedition" involving a fleet of ten spacecraft with 70 crew members that would spend 443 days on the surface of Mars before returning to Earth. The spacecraft, seven passenger ships, and three cargo ships, would all be assembled in Earth orbit using materials supplied by reusable space shuttles. The fleet would use a nitric acid/hydrazine propellant that, although corrosive and toxic, could be stored without refrigeration during the three-year round-trip to Mars. Von Braun calculated the size and weight of each ship, and how much fuel each of them would require for the round trip (5,320,000 metric tons). Hohmann trajectories would be used to move from Earth- to Mars-orbit, and von Braun computed each rocket burn necessary to perform the required manoeuvres.
Note that days active category does not necessarily equate to time in orbit, for example Mars Global Surveyor is expected remain in Mars orbit for 50 years after its arrival. The detection of derelict spacecraft in Mars orbit has some interest due to the minute risk of collision with such a spacecraft and an example of this is a proposal to use the Optical Navigation Camera on the Mars Reconnaissance Orbiter to search for small moons, dust rings, and old orbiters.