Innermost Planets PDF

Solar System GILDEN MAECAH M. MIGALANG Faculty, Science and Research Department Integrated Developmental School, College of Education Mindanao State University - Iligan Institute of Technology Learning Objectives: At the end of the lesson, you should be able to: 1. define a pl...

Solar System GILDEN MAECAH M. MIGALANG Faculty, Science and Research Department Integrated Developmental School, College of Education Mindanao State University - Iligan Institute of Technology Learning Objectives: At the end of the lesson, you should be able to: 1. define a planet 2. describe the planetary characteristics of the members of the solar system 3. identify various space missions to understand the solar system. What is a Planet? The word goes back to the ancient Greek word planēt, and it means "wanderer." A more modern definition can be found in the Merriam-Webster dictionary which defines a planet as "any of the large bodies that revolve around the Sun in the solar system." In 2006, the International Astronomical Union (IAU) - a group of astronomers that names objects in our solar system - agreed on their own definition of the word "planet." This new definition changed caused Pluto's famous "demotion" to a dwarf planet. What is a Planet? The definition of a planet adopted by the IAU says a planet must do three things: It must orbit a star (in our cosmic neighborhood, the Sun). It must be big enough to have enough gravity to force it into a spherical shape. It must be big enough that its gravity has cleared away any other objects of a similar size near its orbit around the Sun. What is a Planet? In 2005, a team of astronomers announced that they had found a tenth planet – it was a KBO similar in size to Pluto. People began to wonder what planethood really means. Just what is a planet, anyway? Suddenly the answer to that question didn't seem so self-evident, and, as it turns out, there are plenty of disagreements about it. The IAU took on the challenge of classifying the newly found KBO, which later was named Eris. In 2006, the IAU passed a resolution that defined the term planet. It also established a new category called dwarf planet. Eris, Ceres, Pluto, and two more recently discovered KBOs named Haumea and Makemake, are the dwarf planets recognized by the IAU. There may be another 100 dwarf planets in the solar system, and hundreds more in and just outside the Kuiper Belt. What is the NEW definition of a Planet? According to IAU’s Resolution B5: Definition of a Planet in the Solar System: 1. A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit. 2. A 'dwarf planet' is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite. 3. All other objects, except satellites, orbiting the Sun shall be referred to collectively as 'Small Solar System Bodies.'" The Inner Planets The first four planets from the Sun are Mercury, Venus, Earth, and Mars. These inner planets also are known as terrestrial planets because they have solid surfaces. The terrestrial planets are small, rocky, dense planets with few or no moon at all. Their rotation about their axes is relatively slow. The terrestrial planets include Mercury, Venus, Earth, and Mars. the rocky planets of the inner solar system consist of magnesium an iron silicate minerals with metallic cores. In the inner solar system solid bodies rich in iron, magnesium, silicon and oxygen formed.  Mercury: The Swift Planet National Aeronautics and Space Administration The smallest planet in our solar system and nearest Mercury to the Sun, Mercury is only slightly larger than Earth's Moon. From the surface of Mercury, the Sun would appear more than three times as large as it does when viewed from Earth, and the sunlight would be as much as seven times brighter. Mercury doesn't have moons and rings. It is known as the Swift Planet because of how fast it travels through space—a whopping 29 miles per second (47 kilometers per second). Luna Mercury: The Swift Planet Mercury's surface temperatures are both extremely hot and cold. Because the planet is so close to the Sun, day temperatures can reach highs of 800°F (430°C). Without an atmosphere to retain that heat at night, temperatures can dip as low as -290°F (-180°C). Despite its proximity to the Sun, Mercury is not the hottest planet in our solar system – that title belongs to nearby Venus, thanks to its dense atmosphere. But Mercury is the fastest planet, zipping around the Sun every 88 Earth days. Mercury’s Size and Distance With a radius of 1,516 miles (2,440 kilometers), Mercury is a little more than 1/3 the width of Earth. If Earth were the size of a nickel, Mercury would be about as big as a blueberry. From an average distance of 36 million miles (58 million kilometers), Mercury is 0.4 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 3.2 minutes to travel from the Sun to Mercury. Mercury’s Potential for Life Mercury's environment is not conducive to life as we know it. The temperatures and solar radiation that characterize this planet are most likely too extreme for organisms to adapt to. Mercury’s Orbit and Rotation Mercury's highly eccentric, egg-shaped orbit takes the planet as close as 29 million miles (47 million kilometers) and as far as 43 million miles (70 million kilometers) from the Sun. It speeds around the Sun every 88 days, traveling through space at nearly 29 miles (47 kilometers) per second, faster than any other planet. Mercury spins slowly on its axis and completes one rotation every 59 Earth days. But when Mercury is moving fastest in its elliptical orbit around the Sun (and it is closest to the Sun), each rotation is not accompanied by sunrise and sunset like it is on most other planets. Mercury’s Orbit and Rotation The morning Sun appears to rise briefly, set, and rise again from some parts of the planet's surface. The same thing happens in reverse at sunset for other parts of the surface. One Mercury solar day (one full day-night cycle) equals 176 Earth days – just over two years on Mercury. Mercury's axis of rotation is tilted just 2 degrees with respect to the plane of its orbit around the Sun. That means it spins nearly perfectly upright and so does not experience seasons as many other planets do. Mercury’s Surface Mercury's surface resembles that of Earth's Moon, scarred by many impact craters resulting from collisions with meteoroids and comets. Craters and features on Mercury are named after famous deceased artists, musicians, or authors, including children's author Dr. Seuss and dance pioneer Alvin Ailey. Very large impact basins, including Caloris (960 miles or 1,550 kilometers in diameter) and Rachmaninoff (190 miles, or 306 kilometers in diameter), were created by asteroid impacts on the planet's surface early in the solar system's history. While there are large areas of smooth terrain, there are also cliffs, some hundreds of miles long and soaring up to a mile high. They rose as the planet's interior cooled and contracted over the Schon, 2011 billions of years since Mercury formed. Mercury’s Structure Mercury is the second densest planet, after Earth. It has a large metallic core with a radius of about 1,289 miles (2,074 kilometers), about 85% of the planet's radius. There is evidence that it is partly molten or liquid. Mercury's outer shell, comparable to Earth's outer shell (called the mantle and crust), is only about 400 kilometers (250 miles) thick. Mercury’s Atmosphere Instead of an atmosphere, Mercury possesses a thin exosphere made up of atoms blasted off the surface by the solar wind and striking meteoroids. Mercury's exosphere is composed mostly of oxygen, sodium, hydrogen, helium, and potassium. Daytime temperatures are significantly warmer than those found on Earth, and both have very thin atmospheres due to insufficient gravity and proximity to the sun. This type of tenuous atmosphere is called an exosphere, which on Mercury extends from space all the way down to the surface of the planet. It is generated mostly by the interaction of the sun with the planetary surface materials, as well as bombardment by meteors from space and the radioactive decay of elements within the crust. Mercury’s Exploration Because Mercury is so close to the Sun, it is hard to directly observe from Earth except during dawn or twilight when the Sun's brightness doesn't outshine little Mercury. Three spacecraft have explored Mercury. Mariner 10. The first spacecraft sent to study Mercury. MESSENGER. The first spacecraft to orbit Mercury. BepiColombo. An international mission comprised of two spacecraft. Mariner 10 Mariner 10 was the first spacecraft sent to the planet Mercury; the first mission to explore two planets (Mercury and Venus) during a single mission; the first to return to its primary destination for another look; and the first to use a gravity assist to change its flight path. Type: Multiple Flybys Launch: November 3, 1973 Returned: January 21, 1974 Target: Mercury and Venus Mariner 10 MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) The first spacecraft to visit Mercury in 30 years, and the first ever to orbit, MESSENGER mapped the entire planet, discovered abundant water ice in shadows at the poles, and unlocked knowledge about Mercury's geology and magnetic field. Type: Orbiter Launch: Aug 2, 2004 Returned: April 30, 2015 Target: Mercury Objective: Mapping and Science Discoveries MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) NASA's MESSENGER spacecraft orbited Mercury for more than four years. Among its accomplishments, the mission determined Mercury’s surface composition, revealed its geological history, discovered details about its internal magnetic field, and verified its polar deposits are dominantly water- ice. The mission ended when MESSENGER slammed into Mercury’s surface. Mar. 11, 2011: MESSENGER finally entered orbit around Mercury nearly seven years after launch Apr. 30, 2015: MESSENGER plunged into Mercury at end of is mission MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) BepiColombo is an international mission comprised of two spacecraft riding together to Mercury to orbit and to study the planet from unique vantage points. What is BepiColombo? BepiColombo is an international mission comprised of two spacecraft riding together to Mercury to orbit and to study the planet from unique vantage points. The European Space Agency (ESA) provided one orbiter. The Japan Aerospace Exploration Agency (JAXA) supplied the second orbiter. BepiColombo launched in October 2018 and is scheduled to begin orbiting Mercury in 2025. ESA's Mercury Planetary Orbiter (MPO) will study the planet's surface and interior. JAXA's Mercury Magnetospheric Orbiter (MIO) will study the planet's magnetic field. These are the first Mercury missions for the ESA and Japan. Only two other spacecraft have visited Mercury: NASA's Mariner 10 and MESSENGER. This color enhanced view of Mercury builds upon the monochrome images of Mercury that have been created using MESSENGER imagery. This new colorful view of Mercury highlights the chemical, mineralogical, and physical differences between the rocks that make up Mercury's surface. Notable Features: Young crater rays, extending radially from fresh impact craters, appear light blue or white. Medium- and dark-blue areas are a geologic unit of Mercury's crust known as the "low-reflectance material", thought to be rich in a dark, opaque mineral. Tan areas are plains formed by eruption of highly fluid lavas. The giant Caloris basin is the large circular tan feature located in the northern hemisphere. Venus: The Morning and the Evening Star National Aeronautics and Space Administration Venus is the second planet from the Sun, and Earth's closest planetary neighbor. Venus is the third brightest object in the sky after the Sun and Moon. Venus spins slowly in the opposite direction from most planets. Venus is similar in structure and size to Earth, and is sometimes called Earth's evil twin. Its thick atmosphere traps heat in a runaway greenhouse effect, making it the hottest planet in our solar system with surface temperatures hot enough to melt lead. Below the dense, persistent clouds, the surface has volcanoes and deformed mountains. Venus: The Morning and the Evening Star National Aeronautics and Space Administration It is far more dazzling than any of the actual stars in the sky and does not appear to twinkle. Instead, it glows with a steady, silvery light. Nicolas Camille Flammarion, a noted French astronomer in the late 19th and early 20th century, referred to Venus as "The Shepherd's Star." Venus can be observed in the morning before sunrise or in the evening after sunset. Namesake The ancient Romans could easily see seven bright objects in the sky: the Sun, the Moon, and the five brightest planets: Mercury, Venus, Mars, Jupiter, and Saturn. They named the objects after their most important gods. Venus is named for the ancient Roman goddess of love and beauty, who was known as Aphrodite to the ancient Greeks. Most features on Venus are named for women. It’s the only planet named after a female god. Venus’ Potential for Life Thirty miles up (about 50 kilometers) from the surface of Venus temperatures range from 86 to 158 Fahrenheit (30 to 70 Celsius). This temperature range could accommodate Earthly life, such as “extremophile” microbes. And atmospheric pressure at that height is similar to what we find on Earth’s surface. At the tops of Venus’ clouds, whipped around the planet by winds measured as high as 224 mph (360 kph), we find another transformation. Persistent, dark streaks appear. Scientists are so far unable to explain why these streaks remain stubbornly intact, even amid hurricane-force winds. They also have the odd habit of absorbing ultraviolet radiation. Venus’ Potential for Life The most likely explanations focus on fine particles, ice crystals, or even a chemical compound called iron chloride. Although it's much less likely, another possibility considered by scientists who study astrobiology is that these streaks could be made up of microbial life, Venus-style. Astrobiologists note that ring-shaped linkages of sulfur atoms, known to exist in Venus’ atmosphere, could provide microbes with a kind of coating that would protect them from sulfuric acid. These handy chemical cloaks would also absorb potentially damaging ultraviolet light and re-radiate it as visible light. Venus’ Potential for Life Some of the Russian Venera probes did, indeed, detect particles in Venus’ lower atmosphere about a micron in length – roughly the same size as a bacterium on Earth. None of these findings provide compelling evidence for the existence of life in Venus’ clouds. But the questions they raise, along with Venus’ vanished ocean, its violently volcanic surface, and its hellish history, make a compelling case for missions to investigate our temperamental sister planet. There is much, it would seem, that she can teach us. Venus’ Size and Distance Venus orbits the Sun from an average distance of 67 million miles (108 million kilometers), or 0.72 astronomical units. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight about six minutes to travel from the Sun to Venus. Earth's nearness to Venus is a matter of perspective. The planet is nearly as big around as Earth. Its diameter at its equator is about 7,521 miles (12,104 kilometers), versus 7,926 miles (12,756 kilometers) for Earth. From Earth, Venus is the brightest object in the night sky after our own Moon. The ancients, therefore, gave it great importance in their cultures, even thinking it was two objects: a morning star and an evening star. That’s where the trick of perspective comes in. Venus’ Size and Distance Because Venus’ orbit is closer to the Sun than ours, the two of them – from our viewpoint – never stray far from each other. The ancient Egyptians and Greeks saw Venus in two guises: first in one orbital position (seen in the morning), then another (your “evening” Venus), just at different times of the year. At its nearest to Earth, Venus is about 24 million (about 38 million kilometers) away. But most of the time the two planets are farther apart. The maximum distance between Venus and Earth is about 162 million miles (261 million kilometers). Mercury, the innermost planet, actually spends more time in Earth’s proximity than Venus. Venus’ Size and Distance One more trick of perspective: how Venus looks through binoculars or a telescope. Keep watch over many months, and you’ll notice that Venus has phases, just like our Moon – full, half, quarter, etc. The complete cycle, however, new to full, takes 584 days, while our Moon takes just a month. And it was this perspective, the phases of Venus first observed by Galileo through his telescope, that provided the key scientific proof for the Copernican heliocentric nature of the solar system. The Phases of Venus – image courtesy of Universe Today Venus’ Orbit and Rotation Spending a day on Venus would be quite a disorienting experience – that is, if your spacecraft or spacesuit could protect you from temperatures in the range of 900 degrees Fahrenheit (475 Celsius). For one thing, your “day” would be 243 Earth days long – longer even than a Venus year (one trip around the Sun), which takes only 225 Earth days. For another, because of the planet's extremely slow rotation, sunrise to sunset would take 117 Earth days. And by the way, the Sun would rise in the west and set in the east, because Venus spins backward compared to Earth. While you’re waiting, don’t expect any seasonal relief from the unrelenting temperatures. On Earth, with its spin axis tilted by about 23 degrees, we experience summer when our part of the planet (our hemisphere) receives the Sun’s rays more directly – a result of that tilt. In winter, the tilt means the rays are less direct. No such luck on Venus: Its very slight tilt is only three degrees, which is too little to produce noticeable seasons. Venus’ Moon Venus is one of only two planets in our solar system that doesn't have a moon, but it does have a quasi-satellite that has officially been named Zoozve. This object was discovered on Nov. 11, 2002, by Brian Skiff at the Lowell Observatory Near-Earth-Object Search (LONEOS) in Flagstaff, Arizona, a project funded by NASA that ended in February 2008. Quasi-satellites, sometimes called quasi-moons, are asteroids that orbit the Sun while staying close to a planet. A quasi-satellite’s orbit usually is more oblong and less stable than the planet's orbit. In time, the shape of a quasi-satellite’s orbit may change and it may move away from the planet. Venus’ Moon After the discovery in 2002, Skiff reported his finding to the Minor Planet Center, which is funded by a Near-Earth Object (NEO) Observations Program grant from NASA’s Planetary Defense Coordination Office. At that time, it was given the provisional name 2002 VE68. Skiff said he didn’t realize the asteroid’s importance and forgot about the object until a radio show host reached out to him in 2023 about naming it Zoozve. Soon after Skiff’s discovery, a team of astronomers, including Seppo Mikkola with the University of Turku in Finland and Paul Wiegert with the University of Western Ontario in London, determined that the object was the first of its kind to be discovered. They think that Zoozve may have been a companion to Venus for at least 7,000 years, and that Earth’s gravity helped push Zoozve into its present orbit. The name Zoozve comes from a child's poster of the solar system. The artist, Alex Foster, saw “2002 VE68” on a list of solar system objects, wrote down “2002 VE,” and then misread his own handwriting as “Zoozve.” Latif Nasser, co-host of the WNYC Studios show Radiolab, tracked down the source of the mistake with the help of Liz Landau, a NASA senior communications specialist. Nasser suggested that Skiff request that the IAU officially name the asteroid Zoozve. Skiff agreed, and the name Zoozve was approved in February 2024. Earth has more than One Moon! According to the International Astronomical Union (IAU), the organization that names space objects, Zoozve is the first-identified quasi-satellite of a major planet. Earth also has quasi-satellites, including a small asteroid discovered in 2016. According to a report by TIME Magazine, astronomers are estimating that 2024 PT5 will be the moon's lunar-like neighbor starting Sept. 29 before it leaves the Earth's gravitational orbit on Nov. 25. It will, however, be barely visible as it would measure only around 10 meters or 33 feet. Earth has more than One Moon! Based on its brightness, scientists at NASA’s Jet Propulsion Laboratory (JPL) estimate Zoozve ranges in size from 660 feet (200 meters) to 1,640 feet (500 meters) across. Interestingly, Zoozve also orbits relatively close to Earth but does not pose a threat to our planet. For the next 175 years, the closest Zoozve will get to Earth is in the year 2149 when it will be about 2.2 million miles (3.5 million kilometers) away, or about 9 times the distance from Earth to the Moon. Venus’ Structure If we could slice Venus and Earth in half, pole to pole, and place them side by side, they would look remarkably similar. Each planet has an iron core enveloped by a hot-rock mantle; the thinnest of skins forms a rocky, exterior crust. On both planets, this thin skin changes form and sometimes erupts into volcanoes in response to the ebb and flow of heat and pressure deep beneath. On Earth, the slow movement of continents over thousands and millions of years reshapes the surface, a process known as “plate tectonics.” Something similar might have happened on Venus early in its history. Today a key element of this process could be operating: subduction, or the sliding of one continental “plate” beneath another, which can also trigger volcanoes. Subduction is believed to be the first step in creating plate tectonics. NASA’s Magellan spacecraft, which ended a five-year mission to Venus in 1994, mapped the broiling surface using radar. Magellan saw a land of extreme volcanism – a relatively young surface, one recently reshaped (in geologic terms), and chains of towering mountains. Venus’ Structure RADAR Imaging of Venus produced by the US Geological Survey Venus’ Surface The Soviet Union sent a series of probes to Venus between 1961 and 1984 as part of its Venera program (Venera is Russian for Venus). Ten probes made it to the surface, and a few functioned briefly after landing. The longest survivor lasted two hours; the shortest, 23 minutes. Photos snapped before the landers fried show a barren, dim, and rocky landscape, and a sky that is likely some shade of sulfur yellow. Volcanoes and tectonic forces appear to have erased most traces of the early surface of Venus. Newer computer models indicate the resurfacing may have happened piecemeal over an extended period of time. The average age of surface features could be as young as 150 million years, with some older surfaces mixed in. Venus’ Surface Venus has valleys and high mountains dotted with thousands of volcanoes. Its surface features – most named for both real and mythical women – include Ishtar Terra, a rocky, highland area around the size of Australia near the north pole, and an even larger, South- America-sized region called Aphrodite Terra that stretches across the equator. One mountain reaches 36,000 feet (11 kilometers), higher than Mt. Everest. Notably, except for Earth, Venus has by far the fewest impact craters of any rocky planet. Venus’ Surface Other notable features of the Venus landscape include: A volcanic crater named Sacajawea for Lewis and Clark’s Native American guide. A deep canyon called Diana for the Roman goddess of the hunt. “Pancake” domes with flat tops and steep sides, as wide as 38 miles (62 kilometers), likely formed by the extrusion of highly viscous lava. “Tick” domes, odd volcanoes with radiating spurs that, from above, make them look like their blood- feeding namesake. Tesserae, terrain with intricate patterns of ridges and grooves that suggest the scorching temperatures make rock behave in some ways more like peanut butter beneath a thin and strong chocolate layer on Venus.  Venus’ Atmosphere Venus’ atmosphere is one of extremes. With the hottest surface in the solar system, apart from the Sun itself, Venus is hotter even than the innermost planet, charbroiled Mercury. The atmosphere is mostly carbon dioxide – the same gas driving the greenhouse effect on Venus and Earth – with clouds composed of sulfuric acid. And at the surface, the hot, high-pressure carbon dioxide behaves in a corrosive fashion. But higher up in the atmosphere, temperatures and pressure begin to ease. Venus’ Magnetosphere Even though Venus is similar in size to Earth and has a similar-sized iron core, the planet does not have its own internally generated magnetic field. Instead, Venus has what is known as an induced magnetic field. This weak magnetic field is created by the interaction of the Sun's magnetic field and the planet's outer atmosphere. Ultraviolet light from the Sun excites gases in Venus' outermost atmosphere; these electrically excited gases are called ions, and thus this region is called the ionosphere (Earth has an ionosphere as well). The solar wind – a million-mile-per-hour gale of electrically charged particles streaming continuously from the Sun – carries with it the Sun's magnetic field. When the Sun's magnetic field interacts with the electrically excited ionosphere of Venus, it creates or induces, a magnetic field there. This induced magnetic field envelops the planet and is shaped like an extended teardrop, or the tail of a comet, as the solar wind blows past Venus and outward into the solar system. Venus’ Exploration Dozens of spacecraft have launched to explore Venus, but not all have been successful. NASA's Mariner 2 was the first spacecraft to visit any planet beyond Earth when it flew past Venus on Dec. 14, 1962. NASA is planning two new missions to Venus: VERITAS, and DAVINCI. Venus’ Exploration NASA has selected two new missions to Venus, Earth’s nearest planetary neighbor. Part of NASA’s Discovery Program, the missions aim to understand how Venus became an inferno-like world when it has so many other characteristics similar to ours – and may have been the first habitable world in the solar system, complete with an ocean and Earth-like climate. DAVINCI+ (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) DAVINCI+ (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) DAVINCI+ will measure the composition of Venus’ atmosphere to understand how it formed and evolved, as well as determine whether the planet ever had an ocean. The mission consists of a descent sphere that will plunge through the planet’s thick atmosphere, making precise measurements of noble gases and other elements to understand why Venus’ atmosphere is a runaway hothouse compared the Earth’s. In addition, DAVINCI+ will return the first high resolution pictures of the unique geological features on Venus known as “tesserae,” which may be comparable to Earth’s continents, suggesting that Venus has plate tectonics. This would be the first U.S.-led mission to Venus’ atmosphere since 1978, and the results from DAVINCI+ could reshape our understanding of terrestrial planet formation in our solar system and beyond. James Garvin of Goddard Space Flight Center in Greenbelt, Maryland, is the principal investigator. Goddard provides project management. VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) VERITAS will map Venus’ surface to determine the planet’s geologic history and understand why it developed so differently than Earth. Orbiting Venus with a synthetic aperture radar, VERITAS will chart surface elevations over nearly the entire planet to create 3D reconstructions of topography and confirm whether processes such as plate tectonics and volcanism are still active on Venus. VERITAS also will map infrared emissions from Venus’ surface to map its rock type, which is largely unknown, and determine whether active volcanoes are releasing water vapor into the atmosphere. Suzanne Smrekar of NASA’s Jet Propulsion Laboratory in Southern California, is the principal investigator. JPL provides project management. The German Aerospace Center will provide the infrared mapper with the Italian Space Agency and France’s Centre National d’Etudes Spatiales contributing to the radar and other parts of the mission. Venus’ Exploration Venus’ Exploration Venus’ Exploration Venus’ Exploration Earth: The Blue Planet National Aeronautics and Space Administration Earth – our home planet – is the third planet from the Sun, and the fifth largest planet. It's the only place we know of inhabited by living things. Length of Day: 23.9 hours Length of Year: 365.25 Days Distance from the Sun: 150, 196, 428 km One Way Light Time to Sun: 8.350022 minutes Earth: Our Home While Earth is only the fifth largest planet in the solar system, it is the only world in our solar system with liquid water on the surface. Just slightly larger than nearby Venus, Earth is the biggest of the four planets closest to the Sun, all of which are made of rock and metal. Earth’s Namesake The name Earth is at least 1,000 years old. All of the planets, except for Earth, were named after Greek and Roman gods and goddesses. However, the name Earth is was taken from Old English and Germanic word, which simply means “the ground.” Earth’s Potential for Life Earth has a very hospitable temperature and mix of chemicals that have made life abundant here. Most notably, Earth is unique in that most of our planet is covered in liquid water, since the temperature allows liquid water to exist for extended periods of time. Earth's vast oceans provided a convenient place for life to begin about 3.8 billion years ago. Some of the features of our planet that make it great for sustaining life are changing due to the ongoing effects of climate change. Why Earth is Habitable? 1. Goldilocks Region Why Earth is Habitable? 2. Presence of Liquid Water Why Earth is Habitable? 3. Magnetic Field Why Earth is Habitable? 4. Friendly Moon Why Earth is Habitable? 5. Solar Energy Why Earth is Habitable? 6. Atmosphere Why Earth is Habitable? 7. Jupiter Earth’s Size and Distance With an equatorial diameter of 7926 miles (12,760 kilometers), Earth is the biggest of the terrestrial planets and the fifth largest planet in our solar system. From an average distance of 93 million miles (150 million kilometers), Earth is exactly one astronomical unit away from the Sun because one astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. This unit provides an easy way to quickly compare planets' distances from the Sun. It takes about eight minutes for light from the Sun to reach our planet. Earth’s Orbit and Rotation As Earth orbits the Sun, it completes one rotation every 23.9 hours. It takes 365.25 days to complete one trip around the Sun. That extra quarter of a day presents a challenge to our calendar system, which counts one year as 365 days. To keep our yearly calendars consistent with our orbit around the Sun, every four years we add one day. That day is called a leap day, and the year it's added to is called a leap year. Earth’s Orbit and Rotation Earth's axis of rotation is tilted 23.4 degrees with respect to the plane of Earth's orbit around the Sun. This tilt causes our yearly cycle of seasons. During part of the year, the northern hemisphere is tilted toward the Sun, and the southern hemisphere is tilted away. With the Sun higher in the sky, solar heating is greater in the north producing summer there. Less direct solar heating produces winter in the south. Six months later, the situation is reversed. When spring and fall begin, both hemispheres receive roughly equal amounts of heat from the Sun. Earth’s Moon Earth is the only planet that has a single moon. Our Moon is the brightest and most familiar object in the night sky. In many ways, the Moon is responsible for making Earth such a great home. It stabilizes our planet's wobble, which has made the climate less variable over thousands of years. Earth sometimes temporarily hosts orbiting asteroids or large rocks. They are typically trapped by Earth's gravity for a few months or years before returning to an orbit around the Sun. Some asteroids will be in a long “dance” with Earth as both orbit the Sun. Earth’s Moon Earth is the only planet that has a single moon. Some moons are bits of rock that were captured by a planet's gravity, but our Moon is likely the result of a collision billions of years ago. When Earth was a young planet, a large chunk of rock smashed into it, displacing a portion of Earth's interior. The resulting chunks clumped together and formed our Moon. With a radius of 1,080 miles (1,738 kilometers), the Moon is the fifth largest moon in our solar system (after Ganymede, Titan, Callisto, and Io). The Moon is an average of 238,855 miles (384,400 kilometers) away from Earth. That means 30 Earth- sized planets could fit in between Earth and its Moon. However, results show that growth is challenging; the lunar regolith plants were slow to develop and many showed severe stress morphologies. Moreover, all plants grown in lunar soils differentially expressed genes indicating ionic stresses, similar to plant reactions to salt, metal and reactive oxygen species. Earth’s Quasi-moons Although mini-moons are usually rare, several have been identified within Earth’s orbit since 2006. In that year, 2006 RH120, the Earth’s first confirmed mini-moon with a diameter of about 2 to 4 meters was captured in Earth’s orbit for roughly a year. This was the only mini-moon to have been photographed. The Southern African Large Telescope (SALT) was used to capture the image of it. It was spotted by the Catalina Sky Survey (CSS) which was established by NASA using telescopes near Tucson, Arizona in 1998 to search for “near-Earth objects”. The 2022 NX1 mini-moon, with a diameter of somewhere between 5 and 15 metres was first seen in 1981, then again in 2022. It is expected to return to Earth’s orbit to take up a horseshoe orbital path again in 2051. Earth’s Quasi-moons The asteroid currently approaching the planet is known as 2024 PT5. It was first spotted on August 7 using the NASA- funded Asteroid Terrestrial-impact Last Alert System (ATLAS) located at the Haleakala Observatory on the island of Maui, Hawaii. seven identified quasi-moons that have elliptical orbits around the Earth. The largest of the quasi-moons that has been identified is Kamo’oalewa or 2016 HO3. It could be as large as 328 feet in diameter and has a fairly stable orbit. Another quais-moon that was recently discovered is 2023 FW13, about the same size as Kamo’oalewa. Are there other types of moon? Also known as Kordylewski clouds, ghost moons are concentrations of dust that are typically found in the Lagrangian points in the Earth-moon system. These Lagrangian points, sometimes known as gravitational “sweet spots”, are where the gravitational forces of the Earth and the moon meet, allowing the ghost moon to maintain a stable position. These clouds can measure as much as 100,000km across and were first discovered by Polish astronomer Kazimierz Kordylewski in the 1960s using a technique called polarimetry, measuring the direction of how light waves vibrate. These dust clouds were later confirmed in 2018 by the Royal Astronomical Society. Earth’s Structure Earth is composed of four main layers, starting with an inner core at the planet's center, enveloped by the outer core, mantle, and crust. The inner core is a solid sphere made of iron and nickel metals about 759 miles (1,221 kilometers) in radius. There the temperature is as high as 9,800 degrees Fahrenheit (5,400 degrees Celsius). Surrounding the inner core is the outer core. This layer is about 1,400 miles (2,300 kilometers) thick, made of iron and nickel fluids. In between the outer core and crust is the mantle, the thickest layer. This hot, viscous mixture of molten rock is about 1,800 miles (2,900 kilometers) thick and has the consistency of caramel. The outermost layer, Earth's crust, goes about 19 miles (30 kilometers) deep on average on land. At the bottom of the ocean, the crust is thinner and extends about 3 miles (5 kilometers) from the seafloor to the top of the mantle. Earth’s Structure Earth’s Surface Like Mars and Venus, Earth has volcanoes, mountains, and valleys. Earth's lithosphere, which includes the crust (both continental and oceanic) and the upper mantle, is divided into huge plates that are constantly moving. Earth's global ocean, which covers nearly 70% of the planet's surface, has an average depth of about 2.5 miles (4 kilometers) and contains 97% of Earth's water. Almost all of Earth's volcanoes are hidden under these oceans. Hawaii's Mauna Kea volcano is taller from base to summit than Mount Everest, but most of it is underwater. Earth's longest mountain range is also underwater, at the bottom of the Arctic and Atlantic oceans. It is four times longer than the Andes, Rockies and Himalayas combined. Earth’s Magnetosphere Our planet's rapid rotation and molten nickel-iron core give rise to a magnetic field, which the solar wind distorts into a teardrop shape in space. (The solar wind is a stream of charged particles continuously ejected from the Sun.) When charged particles from the solar wind become trapped in Earth's magnetic field, they collide with air molecules above our planet's magnetic poles. These air molecules then begin to glow and cause aurorae, or the northern and southern lights. The magnetic field is what causes compass needles to point to the North Pole regardless of which way you turn. But the magnetic polarity of Earth can change, flipping the direction of the magnetic field. The geologic record tells scientists that a magnetic reversal takes place about every 400,000 years on average, but the timing is very irregular. As far as we know, such a magnetic reversal doesn't cause any harm to life on Earth, and a reversal is very unlikely to happen for at least another thousand years. But when it does happen, compass needles are likely to point in many different directions for a few centuries while the switch is being made. And after the switch is completed, they will all point south instead of north. Earth’s Magnetosphere Earth’s Exploration The first scientific discovery in outer space was made in Earth orbit when NASA's Explorer 1 found the Van Allen Radiation Belt in 1958. Since then, Earth has been under constant study. Earth is made up of complex, interactive systems that create a constantly changing world that we are striving to understand. From the vantage point of space, we are able to observe our planet globally, using sensitive instruments to understand the delicate balance among its oceans, air, land, and life. NASA satellite observations help study and predict weather, drought, pollution, climate change, and many other phenomena that affect the environment, economy, and society. Earth’s Exploration NASA studies our own planet more than any other. It operate 26 missions in orbit and sponsor hundreds of research programs and studies each year. It observe our planet’s oceans, land, ice, and atmosphere, and measure how a change in one drives change in others. We develop new ways to observe and study Earth's interconnected systems and we build long-term data records of how our planet evolves. The agency freely shares this unique knowledge and works with institutions around the world. NASA assembles its temperature record, known as the GISS Surface Temperature Analysis (GISTEMP), from surface air temperature data acquired by tens of thousands of meteorological stations, as well as sea surface temperatures from ship- and buoy-based instruments. It also includes measurements from Antarctica. Analytical methods consider the varied spacing of temperature stations around the globe and urban heating effects that could skew the calculations. The GISTEMP analysis calculates temperature anomalies rather than absolute temperature. A temperature anomaly shows how far the temperature has departed from the 1951 to 1980 base average.  Possible Habitable Planets National Aeronautics and Space Administration An exoplanet is any planet beyond our solar system. Most of them orbit other stars, but some free-floating exoplanets, called rogue planets, are untethered to any star. NASA has confirmed more than 5,600 exoplanets out of the billions that were believed to exist. Possible Habitable Planets  Mars: The Red Planet National Aeronautics and Space Administration Mars – the fourth planet from the Sun – is a dusty, cold, desert world with a very thin atmosphere. This dynamic planet has seasons, polar ice caps, extinct volcanoes, canyons and weather. Mars is one of the most explored bodies in our solar system, and it's the only planet where we've sent rovers to roam the alien landscape. NASA missions have found lots of evidence that Mars was much wetter and warmer, with a thicker atmosphere, billions of years ago.  Mars’ Namesake Mars was named by the ancient Romans for their god of war because its reddish color was reminiscent of blood. Other civilizations also named the planet for this attribute – for example, the Egyptians called it "Her Desher," meaning "the red one." Even today, it is frequently called the "Red Planet" because iron minerals in the Martian dirt oxidize, or rust, causing the surface to look red. Mars’ Potential for Life Scientists don't expect to find living things currently thriving on Mars. Instead, they're looking for signs of life that existed long ago, when Mars was warmer and covered with water. Mars’ Size and Distance With a radius of 2,106 miles (3,390 kilometers), Mars is about half the size of Earth. From an average distance of 142 million miles (228 million kilometers), Mars is 1.5 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 13 minutes to travel from the Sun to Mars. Mars’ Orbit and Rotation As Mars orbits the Sun, it completes one rotation every 24.6 hours, which is very similar to one day on Earth (23.9 hours). Martian days are called sols – short for "solar day." A year on Mars lasts 669.6 sols, which is the same as 687 Earth days. Mars' axis of rotation is tilted 25 degrees with respect to the plane of its orbit around the Sun. This is another similarity with Earth, which has an axial tilt of 23.4 degrees. Like Earth, Mars has distinct seasons, but they last longer than seasons here on Earth since Mars takes longer to orbit the Sun (because it's farther away). And while here on Earth the seasons are evenly spread over the year, lasting 3 months (or one quarter of a year), on Mars the seasons vary in length because of Mars' elliptical, egg-shaped orbit around the Sun. Spring in the northern hemisphere (autumn in the southern) is the longest season at 194 sols. Autumn in the northern hemisphere (spring in the southern) is the shortest at 142 days. Northern winter/southern summer is 154 sols, and northern summer/southern winter is 178 sols. Mars’ Moons Mars has two small moons, Phobos and Deimos, that may be captured asteroids. They're potato-shaped because they have too little mass for gravity to make them spherical. The moons get their names from the horses that pulled the chariot of the Greek god of war, Ares. Phobos, the innermost and larger moon, is heavily cratered, with deep grooves on its surface. It is slowly moving towards Mars and will crash into the planet or break apart in about 50 million years. Deimos is about half as big as Phobos and orbits two and a half times farther away from Mars. Oddly-shaped Deimos is covered in loose dirt that often fills the craters on its surface, making it appear smoother than pockmarked Phobos. Mars’ Rings Mars has no rings. However, in 50 million years when Phobos crashes into Mars or breaks apart, it could create a dusty ring around the Red Planet. Mars’ Surface The Red Planet is actually many colors. At the surface, we see colors such as brown, gold, and tan. The reason Mars looks reddish is due to oxidization – or rusting – of iron in the rocks, regolith (Martian “soil”), and dust of Mars. This dust gets kicked up into the atmosphere and from a distance makes the planet appear mostly red. Interestingly, while Mars is about half the diameter of Earth, its surface has nearly the same area as Earth’s dry land. Its volcanoes, impact craters, crustal movement, and atmospheric conditions such as dust storms have altered the landscape of Mars over many years, creating some of the solar system's most interesting topographical features. Mars’ Surface A large canyon system called Valles Marineris is long enough to stretch from California to New York – more than 3,000 miles (4,800 kilometers). This Martian canyon is 200 miles (320 kilometers) at its widest and 4.3 miles (7 kilometers) at its deepest. That's about 10 times the size of Earth's Grand Canyon. Mars is home to the largest volcano in the solar system, Olympus Mons. It's three times taller than Earth's Mt. Everest with a base the size of the state of New Mexico. Mars’ Surface Mars is home to the largest volcano in the solar system, Olympus Mons. It's three times taller than Earth's Mt. Everest with a base the size of the state of New Mexico. In total, it is approximately 10,205m (33481 feet) in height, taller than Mount Everest's 8,849m (29032 feet). Over half of Mauna Kea is underwater in the Pacific Ocean. Around 6,000 metres of the mountain is under the sea, with 4,205 metres above sea level. In total, Mauna Kea is around 1.4km taller than Everest. Mars’ Surface Mars appears to have had a watery past, with ancient river valley networks, deltas, and lakebeds, as well as rocks and minerals on the surface that could only have formed in liquid water. Some features suggest that Mars experienced huge floods about 3.5 billion years ago. There is water on Mars today, but the Martian atmosphere is too thin for liquid water to exist for long on the surface. Today, water on Mars is found in the form of water-ice just under the surface in the polar regions as well as in briny (salty) water, which seasonally flows down some hillsides and crater walls. Mars’ Atmosphere Mars has a thin atmosphere made up mostly of carbon dioxide, nitrogen, and argon gases. To our eyes, the sky would be hazy and red because of suspended dust instead of the familiar blue tint we see on Earth. Mars' sparse atmosphere doesn't offer much protection from impacts by such objects as meteorites, asteroids, and comets. The temperature on Mars can be as high as 70 degrees Fahrenheit (20 degrees Celsius) or as low as about -225 degrees Fahrenheit (-153 degrees Celsius). And because the atmosphere is so thin, heat from the Sun easily escapes this planet. If you were to stand on the surface of Mars on the equator at noon, it would feel like spring at your feet (75 degrees Fahrenheit or 24 degrees Celsius) and winter at your head (32 degrees Fahrenheit or 0 degrees Celsius). Occasionally, winds on Mars are strong enough to create dust storms that cover much of the planet. After such storms, it can be months before all of the dust settles. Mars’ Exploration Mars is the only planet we know of inhabited entirely by robots. Each robotic explorer sent to the Red Planet has its own unique capabilities driven by science. Many attributes of a rover take on human-like features, such as “heads,” “bodies,” and “arms and legs." Mars’ Exploration Mars’ Exploration Mars’ Exploration Mars’ Exploration Mars’ Exploration Mars’ Exploration