Did you know that our planet is surrounded by giant,
donut-shaped clouds of radiation?
Here’s what you need to know.
1. The radiation
belts are a side effect of Earth’s magnetic field
The Van Allen radiation belts exist because fast-moving charged
particles get trapped inside Earth’s natural magnetic field, forming two
concentric donut-shaped clouds of radiation. Other planets with global magnetic
Jupiter, also have radiation belts.
2. The radiation
belts were one of our first Space Age discoveries
Earth’s radiation belts were first
identified in 1958 by Explorer 1, the first U.S. satellite. The
inner belt, composed predominantly of protons, and the outer belt, mostly
electrons, would come to be named the Van Allen Belts, after James Van Allen,
the scientist who led the charge designing the instruments and studying the
radiation data from Explorer 1.
3. The Van Allen
Probes have spent six years exploring the radiation belts
In 2012, we launched the twin Van Allen Probes to
study the radiation belts. Over the past six years, these spacecraft have
orbited in and out of the belts, providing brand-new data about how the
radiation belts shift and change in response to solar activity and other
4. Surprise! Sometimes
there are three radiation belts
Shortly after launch, the Van Allen Probes detected a
radiation belt, created by a bout of strong solar activity. All the
extra energy directed towards Earth meant that some particles trapped in our
planet’s magnetic field were swept out into the usually relatively empty region
between the two Van Allen Belts, creating an additional radiation belt.
5. Swan song for the
Van Allen Probes
Originally designed for a two-year mission, the Van Allen
Probes have spent more than six years collecting data in the harsh radiation
environment of the Van Allen Belts. In spring 2019, we’re changing their orbit to bring the perigee — the part of the
orbit where the spacecraft are closest to Earth — about 190 miles lower. This
ensures that the spacecraft will eventually burn up in Earth’s atmosphere,
instead of orbiting forever and becoming space junk.
Because the Van Allen Probes have proven to be so hardy,
they’ll continue collecting data throughout the final months of the mission
until they run out of fuel. As they skim through the outer reaches of Earth’s
atmosphere, scientists and engineers will also learn more about how atmospheric
oxygen can degrade satellite measurements — information that can help build
better satellites in the future.
Our solar system was built on impacts — some big, some small — some fast, some slow. This week, in honor of a possible newly-discovered large crater here on Earth, here’s a quick run through of some of the more intriguing impacts across our solar system.
1. Mercury: A Basin Bigger Than Texas
Mercury does not have a thick atmosphere to protect it from space debris. The small planet is riddled with craters, but none as spectacular as the Caloris Basin. “Basin” is what geologists call craters larger than about 186 miles (300 kilometers) in diameter. Caloris is about 950 miles (1,525 kilometers) across and is ringed by mile-high mountains.
For scale, the state of Texas is 773 miles (1,244 kilometers) wide from east to west.
2. Venus: Tough on Space Rocks
Venus’ ultra-thick atmosphere finishes off most meteors before they reach the surface. The planet’s volcanic history has erased many of its craters, but like almost any place with solid ground in our solar system, there are still impact scars to be found. Most of what we know of Venus’ craters comes from radar images provided by orbiting spacecraft, such as NASA’s Magellan.
Mead Crater is the largest known impact site on Venus. It is about 170 miles (275 kilometers) in diameter. The relatively-flat, brighter inner floor of the crater indicates it was filled with impact melt and/or lava.
3. Earth: Still Craters After All These Years
Evidence of really big impacts — such as Arizona’s Meteor Crater — are harder to find on Earth. The impact history of our home world has largely been erased by weather and water or buried under lava, rock or ice. Nonetheless, we still find new giant craters occasionally.
This follows the finding, announced in November 2018, of a 19-mile (31-kilometer) wide crater beneath Hiawatha Glacier – the first meteorite impact crater ever discovered under Earth’s ice sheets.
If the second crater, which has a width of over 22 miles (35 kilometers), is ultimately confirmed as the result of a meteorite impact, it will be the 22nd largest impact crater found on Earth.
4. Moon: Our Cratered Companion
Want to imagine what Earth might look like without its protective atmosphere, weather, water and other crater-erasing features? Look up at the Moon. The Moon’s pockmarked face offers what may be humanity’s most familiar view of impact craters.
One of the easiest to spot is Tycho, the tight circle and bright, radiating splat are easy slightly off center on the lower-left side of the full moon. Closer views of the 53-mile (85 kilometer)-wide crater from orbiting spacecraft reveal a beautiful central peak, topped with an intriguing boulder that would fill about half of a typical city block.
5. Mars: Still Taking Hits
Mars has just enough atmosphere to ensure nail-biting spacecraft landings, but not enough to prevent regular hits from falling space rocks. This dark splat on the Martian south pole is less than a year old, having formed between July and September 2018. The two-toned blast pattern tells a geologic story. The larger, lighter-colored blast pattern could be the result of scouring by winds from the impact shockwave on ice. The darker-colored inner blast pattern is because the impactor penetrated the thin ice layer, blasting the dark sand underneath in all directions.
6. Ceres: What Lies Beneath
The bright spots in Ceres’ Occator crater intrigued the world from the moment the approaching Dawn spacecraft first photographed it in 2015. Closer inspection from orbit revealed the spots to be the most visible example of hundreds of bright, salty deposits that decorate the dwarf planet like a smattering of diamonds. The science behind these bright spots is even more compelling: they are mainly sodium carbonate and ammonium chloride that somehow made their way to the surface in a slushy brine from within or below the crust. Thanks to Dawn, scientists have a better sense of how these reflective areas formed and changed over time — processes indicative of an active, evolving world.
7. Comet Tempel 1: We Did It!
Scientists have long known we can learn a lot from impact craters — so, in 2005, they made one themselves and watched it happen.
On July 4, 2005, NASA’s Deep Impact spacecraft trained its instruments on an 816-pound (370-kilogram) copper impactor as it smashed into comet Tempel 1.
One of the more surprising findings: The comet has a loose, “fluffy” structure, held together by gravity and contains a surprising amount of organic compounds that are part of the basic building blocks of life.
8. Mimas: May the 4th Be With You
Few Star Wars fans — us included — can resist Obi Wan Kenobi’s memorable line “That’s no moon…” when images of Saturn’s moon Mimas pop up on a screen. Despite its Death Star-like appearance, Mimas is most definitely a moon. Our Cassini spacecraft checked, a lot — and the superlaser-looking depression is simply an 81-mile (130-kilometer) wide crater named for the moon’s discoverer, William Herschel.
9. Europa: Say What?
The Welsh name of this crater on Jupiter’s ocean moon Europa looks like a tongue-twister, but it is easiest pronounced as “pool.” Pwyll is thought to be one of the youngest features we know of on Europa. The bright splat from the impact extends more than 600 miles (about 1,000 kilometers) around the crater, a fresh blanket over rugged, older terrain. “Fresh,” or young, is a relative term in geology; the crater and its rays are likely millions of years old.
10. Show Us Your Greatest Hits
Got a passion for Stickney, the dominant bowl-shaped crater on one end of Mars’ moon Phobos? Or a fondness for the sponge-like abundance of impacts on Saturn’s battered moon Hyperion (pictured)? There are countless craters to choose from. Share your favorites with us on Twitter, Instagram and Facebook.
We’ve discovered thousands of exoplanets – planets beyond our solar system – so far. These worlds are mysterious, but observations from telescopes on the ground and in space help us understand what they might look like.
Take the planet 55 Cancri e, for instance. It’s relatively close, galactically speaking, at 41 light-years away. It’s a rocky planet, nearly two times bigger than Earth, that whips around its star every 18 hours (as opposed to the 365 days it takes our planet to orbit the Sun. Slacker).
The planet’s star, 55 Cancri, is slightly smaller than our Sun, but it’s 65 times closer than the Sun is to Earth. Imagine a massive sun on the horizon! Because 55 Cancri e is so close to its star, it’s tidally locked just like our Moon is to the Earth. One side is always bathed in daylight, the other is in perpetual darkness. It’s also hot. Really hot. So hot that silicate rocks would melt into a molten ocean of melted rock. IT’S COVERED IN AN OCEAN OF LAVA. So, it’s that hot (between 3,140 degrees and 2,420 degrees F).
Scientists think 55 Cancri e also may harbor a thick atmosphere that circulates heat from the dayside to the nightside. Silicate vapor in the atmosphere could condense into sparkling clouds on the cooler, darker nightside that would reflect the lava below. It’s also possible that it would rain sand on the nightside, but … sparkling skies!
Check out our Exoplanet Travel Bureau’s latest 360-degree visualization of 55 Cancri e and download the travel poster at https://go.nasa.gov/2HOyfF3.
Tonight, Australians, Africans, Europeans, Asians and South Americans will have the opportunity to see the longest lunar eclipse of the century. Sorry North America.
Lunar eclipses occur about 2-4 times per year, when the Moon passes into the Earth’s shadow. In order to see a lunar eclipse, you must be on the night side of the Earth, facing the Moon, when the Earth passes in between the Moon and the Sun. Need help visualizing this? Here you go:
What’s the difference between a solar eclipse and a lunar eclipse?
An easy way to remember the difference between a solar eclipse and a lunar eclipse is that the word ‘eclipse’ refers to the object that is being obscured. During a solar eclipse, the Moon blocks the Sun from view. During a lunar eclipse, the Earth’s shadow obscures the Moon.
Why does the Moon turn red?
You may have heard the term ‘Blood Moon’ for a lunar eclipse. When the Moon passes into the Earth’s shadow, it turns red. This happens for the exact same reason that our sunrises and sunsets here on Earth are brilliant shades of pinks and oranges. During a lunar eclipse, the only light reaching the Moon passes through the Earth’s atmosphere. The bluer, shorter wavelength light scatters and the longer wavelength red light passes through and makes it to the Moon.
What science can we learn from a lunar eclipse?
“During a lunar eclipse, the temperature swing is so dramatic that it’s as if the surface of the Moon goes from being in an oven to being in a freezer in just a few hours,” said Noah Petro, project scientist for our Lunar Reconnaissance Orbiter, or LRO, at our Goddard Space Flight Center in Greenbelt, Maryland.
The Diviner team from LRO measures temperature changes on the Moon through their instrument on the spacecraft as well as through a thermal camera on Earth. How quickly or slowly the lunar surface loses heat helps scientists determine characteristics of lunar material, including its composition and physical properties.
When is the next lunar eclipse?
North Americans, don’t worry. If skies are clear, you can see the next lunar eclipse on January 21, 2019. The eclipse will be visible to North Americans, South Americans, and most of Africa and Europe.
Each day, the station completes 16 orbits of our home planet as the six humans living and working aboard our orbiting laboratory conduct important science and research. Their work will not only benefit life here on Earth, but will help us venture deeper into space than ever before.
Our Juno mission arrived at the King of Planets in July 2016. The intrepid robotic explorer has been revealing Jupiter’s secrets ever since.
Here are 10 historic Juno mission highlights:
1. Arrival at a Colossus
After an odyssey of almost five years and 1.7 billion miles (2.7 billion kilometers), our Juno spacecraft fired its main engine to enter orbit around Jupiter on July 4, 2016. Juno, with its suite of nine science instruments, was the first spacecraft to orbit the giant planet since the Galileo mission in the 1990s. It would be the first mission to make repeated excursions close to the cloud tops, deep inside the planet’s powerful radiation belts.
2. Science, Meet Art
Juno carries a color camera called JunoCam. In a remarkable first for a deep space mission, the Juno team reached out to the general public not only to help plan which pictures JunoCam would take, but also to process and enhance the resulting visual data. The results include some of the most beautiful images in the history of space exploration.
3. A Whole New Jupiter
It didn’t take long for Juno—and the science teams who hungrily consumed the data it sent home—to turn theories about how Jupiter works inside out. Among the early findings: Jupiter’s poles are covered in Earth-sized swirling storms that are densely clustered and rubbing together. Jupiter’s iconic belts and zones were surprising, with the belt near the equator penetrating far beneath the clouds, and the belts and zones at other latitudes seeming to evolve to other structures below the surface.
4. The Ultimate Classroom
The Goldstone Apple Valley Radio Telescope (GAVRT) project, a collaboration among NASA, JPL and the Lewis Center for Educational Research, lets students do real science with a large radio telescope. GAVRT data includes Jupiter observations relevant to Juno, and Juno scientists collaborate with the students and their teachers.
5. Spotting the Spot
Measuring in at 10,159 miles (16,350 kilometers) in width (as of April 3, 2017) Jupiter’s Great Red Spot is 1.3 times as wide as Earth. The storm has been monitored since 1830 and has possibly existed for more than 350 years. In modern times, the Great Red Spot has appeared to be shrinking. In July 2017, Juno passed directly over the spot, and JunoCam images revealed a tangle of dark, veinous clouds weaving their way through a massive crimson oval.
“For hundreds of years scientists have been observing, wondering and theorizing about Jupiter’s Great Red Spot,” said Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio. “Now we have the best pictures ever of this iconic storm. It will take us some time to analyze all the data from not only JunoCam, but Juno’s eight science instruments, to shed some new light on the past, present and future of the Great Red Spot.”
6. Beauty Runs Deep
Data collected by the Juno spacecraft during its first pass over Jupiter’s Great Red Spot in July 2017 indicate that this iconic feature penetrates well below the clouds. The solar system’s most famous storm appears to have roots that penetrate about 200 miles (300 kilometers) into the planet’s atmosphere.
7. Powerful Auroras, Powerful Mysteries
Scientists on the Juno mission observed massive amounts of energy swirling over Jupiter’s polar regions that contribute to the giant planet’s powerful auroras – only not in ways the researchers expected. Examining data collected by the ultraviolet spectrograph and energetic-particle detector instruments aboard Juno, scientists observed signatures of powerful electric potentials, aligned with Jupiter’s magnetic field, that accelerate electrons toward the Jovian atmosphere at energies up to 400,000 electron volts. This is 10 to 30 times higher than the largest such auroral potentials observed at Earth.
Jupiter has the most powerful auroras in the solar system, so the team was not surprised that electric potentials play a role in their generation. What puzzled the researchers is that despite the magnitudes of these potentials at Jupiter, they are observed only sometimes and are not the source of the most intense auroras, as they are at Earth.
8. Heat from Within
Juno scientists shared a 3D infrared movie depicting densely packed cyclones and anticyclones that permeate the planet’s polar regions, and the first detailed view of a dynamo, or engine, powering the magnetic field for any planet beyond Earth (video above). Juno mission scientists took data collected by the spacecraft’s Jovian InfraRed Auroral Mapper (JIRAM) instrument and generated a 3D fly-around of the Jovian world’s north pole.
Imaging in the infrared part of the spectrum, JIRAM captures light emerging from deep inside Jupiter equally well, night or day. The instrument probes the weather layer down to 30 to 45 miles (50 to 70 kilometers) below Jupiter’s cloud tops.
9. A Highly Charged Atmosphere
Powerful bolts of lightning light up Jupiter’s clouds. In some ways its lightning is just like what we’re used to on Earth. In other ways,it’s very different. For example, most of Earth’s lightning strikes near the equator; on Jupiter, it’s mostly around the poles.
10. Extra Innings
In June, we approved an update to Juno’s science operations until July 2021. This provides for an additional 41 months in orbit around. Juno is in 53-day orbits rather than 14-day orbits as initially planned because of a concern about valves on the spacecraft’s fuel system. This longer orbit means that it will take more time to collect the needed science data, but an independent panel of experts confirmed that Juno is on track to achieve its science objectives and is already returning spectacular results. The spacecraft and all its instruments are healthy and operating nominally.
Read the full web version of this week’s ‘Solar System: 10 Things to Know’ article HERE.