Why Isn’t Every Year the Warmest Year on Record?

This just in: 2022 effectively tied for the fifth warmest year since 1880, when our record starts. Here at NASA, we work with our partners at NOAA to track temperatures across Earth’s entire surface, to keep a global record of how our planet is changing.

Overall, Earth is getting hotter.

The warming comes directly from human activities – specifically, the release of greenhouse gases like carbon dioxide from burning fossil fuels. We started burning fossil fuels in earnest during the Industrial Revolution. Activities like driving cars and operating factories continue to release greenhouse gases into our atmosphere, where they trap heat in the atmosphere.

So…if we’re causing Earth to warm, why isn’t every year the hottest year on record?

As 2022 shows, the current global warming isn’t uniform. Every single year isn’t necessarily warmer than every previous year, but it is generally warmer than most of the preceding years. There’s a warming trend.

Earth is a really complex system, with various climate patterns, solar activity, and events like volcanic eruptions that can tip things slightly warmer or cooler.

Climate Patterns

While 2021 and 2022 continued a global trend of warming, they were both a little cooler than 2020, largely because of a natural phenomenon known as La Niña.

La Niña is one third of a climate phenomenon called El Niño Southern Oscillation, also known as ENSO, which can have significant effects around the globe. During La Niña years, ocean temperatures in the central and eastern Pacific Ocean cool off slightly. La Niña’s twin, El Niño brings warmer temperatures to the central and eastern Pacific. Neutral years bring ocean temperatures in the region closer to the average.

El Niño and La Niña affect more than ocean temperatures – they can bring changes to rainfall patterns, hurricane frequency, and global average temperature.

We’ve been in a La Niña mode the last three, which has slightly cooled global temperatures. That’s one big reason 2021 and 2022 were cooler than 2020 – which was an El Niño year.

Overall warming is still happening. Current El Niño years are warmer than previous El Niño years, and the same goes for La Niña years. In fact, enough overall warming has occurred that most current La Niña years are warmer than most previous El Niño years. This year was the warmest La Niña year on record.

Solar Activity

Our Sun cycles through periods of more and less activity, on a schedule of about every 11 years. Here on Earth, we might receive slightly less energy — heat — from the Sun during quieter periods and slightly more during active periods.

At NASA, we work with NOAA to track the solar cycle. We kicked off a new one – Solar Cycle 25 – after solar minimum in December 2019. Since then, solar activity has been slightly ramping up.

Because we closely track solar activity, we know that over the past several decades, solar activity hasn't been on the rise, while greenhouse gases have. More importantly, the "fingerprints" we see on the climate, including temperature changes in the upper atmosphere, don't fit the what we'd expect from solar-caused warming. Rather they look like what we expect from increased greenhouse warming, verifying a prediction made decades ago by NASA.

Volcanic Eruptions

Throughout history, volcanoes have driven major shifts in Earth’s climate. Large eruptions can release water vapor — a greenhouse gas like carbon dioxide — which traps additional warmth within our atmosphere.

On the flip side, eruptions that loft lots of ash and soot into the atmosphere can temporarily cool the climate slightly, by reflecting some sunlight back into space.

Like solar activity, we can monitor volcanic eruptions and tease out their effect on variations in our global temperature.

At the End of the Day, It’s Us

Our satellites, airborne missions, and measurements from the ground give us a comprehensive picture of what’s happening on Earth every day. We also have computer models that can skillfully recreate Earth’s climate.

By combining the two, we can see what would happen to global temperature if all the changes were caused by natural forces, like volcanic eruptions or ENSO. By looking at the fingerprints each of these climate drivers leave in our models, it’s perfectly clear: The current global warming we’re experiencing is caused by humans.

For more information about climate change, visit climate.nasa.gov.

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Earth Day at Home with NASA

When you think about Earth Day, you might think about planting trees or picking up garbage. But right now, as a lot of us are staying inside to stay safe, we’ve got you covered for Earth Day at Home with ways to appreciate our beautiful home planet from your couch.

Want to help our researchers map coral in the ocean?

Our new NeMo-Net app lets you do that while playing a game!

What about virtually exploring our planet?

Worldview lets you choose any location on Earth and see it the way our satellites do – in natural color, lit by electric lights at night, or in infrared, highlighting fires around the globe. 

On April 22 -- Earth Day -- we’ll have a host of activities you can participate in. Scientists will share their research from their own homes, including messages from astronauts living on the International Space Station! Hear stories from a trip to Earth’s most remote location: Antarctica, including what happens when the chocolate goes missing on a weeks-long excursion. We’ll even have a new episode of NASA Science Live sharing some of what we’re doing to make our work more sustainable.

We’ll be sharing Earth Day from our homes with #EarthDayAtHome on Twitter, Instagram, Facebook and with a Tumblr Answer Time right here! Follow along, and participate, as we share our love for our home planet with you.

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“Only in the darkness can you see the stars.” —Martin Luther King, Jr.‎ Pause for a moment and take in the vastness and beauty of our home planet captured from the vantage point of space. On this spaceship we call Earth, we are all in this together. 💙 

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NASA’s 60th Anniversary: Home, Sweet Home

Earth is a complex, dynamic system. For 60 years, we have studied our changing planet, and our understanding continues to expand with the use of new technologies. With data from satellites, instruments on the International Space Station, airborne missions, balloons, and observations from ships and on land, we track changes to land, water, ice, and the atmosphere. Application of our Earth observations help improve life now and for future generations. Since we opened for business on Oct. 1, 1958, our history tells a story of exploration, innovation and discoveries. The next 60 years, that story continues. Learn more: https://www.nasa.gov/60

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Discover NASA Technology in Your Life

Have you ever wondered how space exploration impacts you? “Spinoffs” are products and services developed from NASA technology or improved through NASA partnerships. These innovations—first created to help explore space and study Earth—are responsible for billions of dollars in both revenue and saved costs, tens of thousands of jobs created, and for changing the world around us.

Our NASA Home & City interactive web platform allows you to explore some of the spinoff technologies you can find in your everyday life, demonstrating the wider benefits of America’s investments in its space program.

Here are the seven most unexpected items you can find in your homes and cities which were “spun off” from technologies to enable the study and exploration of space.

1. Wireless Headsets

“That’s one small step for man, one giant leap for mankind.” On July 20, 1969, millions were glued to their television sets when NASA astronaut Neil Armstrong offered these famous words via live broadcast, upon becoming the first man to ever step foot on the Moon. This historic transmission was delivered from Armstrong’s headset to the headsets of Mission Control personnel at NASA, and then on to the world.

Improved by the technology that carried Neil Armstrong’s words, more compact and comfortable headsets were developed for airline pilots in the 1960s and '70s. Today those advancements continue to evolve in all forms of communications and telephone equipment. Mobile headsets provide greater efficiency and flexibility for everyone from professionals to video gamers.

2. Water Quality Monitoring

On the International Space Station very little goes to waste. This includes water, which is recovered from every possible source, cleaned and recycled.

Following our development of a simplified bacteria test for water quality on the space station, one engineer created a foundation to distribute test kits suitable for use in rural communities around the world. Water contamination is still a major problem in many places, and the test helps local communities and governments obtain and share water quality data using a smartphone app.

3. Skin Cream

We know that on Earth, gravity is a constant. For astronauts in orbit, however, it’s a different story—and according to a scientist at NASA's Johnson Space Center, studying what happens to bodies in microgravity “can lead to significant new discoveries in human biology for the benefit of humankind.”

As our researchers experimented with replicating microgravity conditions in the lab, they invented a bioreactor that could help simulate conditions that human cells experience in a space-like environment. This allowed them to perform tissue-growth experiments on the ground and in space, and eventually, to consider the question of how to protect human cells from the toxic effects of long-duration space missions.

Now, thanks to this NASA-patented bioreactor, one company uses agents from human cells that produce collagen to enrich its skin cream products. Lab tests have shown the rejuvenating cream to increase skin moisture content by 76 percent and reduce darkness and wrinkles by more than 50 percent.

4. Acoustic Guitars

From its start, NASA has innovated in all branches of aeronautics, which has led to numerous advances in helicopters, including ways to limit vibrations as they fly and advanced composites to build tougher, safer vehicles. 

An industrious helicopter manufacturer that built up its expertise with NASA contracts later used the same special vibration analysis equipment to enhance the sound of acoustic guitars. The company also built the body out of a fiberglass composite used for rotor blades. The resulting instruments are stronger and less expensive to produce than those of traditional rosewood and produce a rich, full sound.

5. Tiny [Mobile] Homes

While the International Space Station is the largest spacecraft ever flown—it's about the size of a football field—living and working space for astronauts is still at a premium. NASA created a studio called the Habitability Design Center to experiment with the interior design of spacecraft to maximize usable space and make scientific research as efficient and effective as possible.

An architect who helped NASA design the interior of the International Space Station launched a company specializing in compact trailers for camping and exploration. Suitable for a full hookup campsite or going completely off-grid, the company's flagship trailer can accommodate two adults and two children for sleeping and can be customized with a range of features including a shower, refrigerator, toilet, and more. And it all fits into a unit light enough to be towed by a four-cylinder car.

6. Blue Light Blocking Ski Goggles

Skiers and snowboarders face extremely bright sunlight, especially when it's reflected off the white snow. That can make it hard to see, and not just because of glare. The blue in sunlight makes it more difficult to discern colors at the edge of the visible light spectrum, like reds. A NASA-designed filter used in snow goggles helps block up to 95 percent of blue light, making it easier for people on the slopes to see the terrain clearly.

7. Implants for the Hearing Impaired

Hearing aids, which make sound louder, can only do so much for those who were born or have become deaf. Cochlear implants work in a completely different way, converting sound into digital signals that can be processed by the brain.  And the technology traces back in part to a NASA space shuttle engineer who used skills in electronics instrumentation and his own experiences with hearing loss to develop an early version of the life-changing device.

These are just a few examples of thousands of NASA Spinoff and dual-purpose technologies benefiting the world around us. 

Trace space back to you and visit NASA Home and City today!

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Earth from Afar

“It suddenly struck me that that tiny pea, pretty and blue, was the Earth. I put up my thumb and shut one eye, and my thumb blotted out the planet Earth. I didn't feel like a giant. I felt very, very small.” - Neil Armstrong, Apollo 11

This week we're celebrating Earth Day 2018 with some of our favorite images of Earth from afar...

At 7.2 million Miles...and 4 Billion Miles

Voyager famously captured two unique views of our homeworld from afar. One image, taken in 1977 from a distance of 7.3 million miles (11.7 million kilometers) (above), showed the full Earth and full Moon in a single frame for the first time in history. The second (below), taken in 1990 as part of a “family portrait of our solar system from 4 billion miles (6.4 billion kilometers), shows Earth as a tiny blue speck in a ray of sunlight.” This is the famous “Pale Blue Dot” image immortalized by Carl Sagan.

“This was our willingness to see the Earth as a one-pixel object in a far greater cosmos,” Sagan’s widow, Ann Druyan said of the image. “It's that humility that science gives us. That weans us from our childhood need to be the center of things. And Voyager gave us that image of the Earth that is so heart tugging because you can't look at that image and not think of how fragile, how fragile our world is. How much we have in common with everyone with whom we share it; our relationship, our relatedness, to everyone on this tiny pixel."

A Bright Flashlight in a Dark Sea of Stars

Our Kepler mission captured Earth’s image as it slipped past at a distance of 94 million miles (151 million kilometers). The reflection was so extraordinarily bright that it created a saber-like saturation bleed across the instrument’s sensors, obscuring the neighboring Moon.

Hello and Goodbye

This beautiful shot of Earth as a dot beneath Saturn’s rings was taken in 2013 as thousands of humans on Earth waved at the exact moment the spacecraft pointed its cameras at our home world. Then, in 2017, Cassini caught this final view of Earth between Saturn’s rings as the spacecraft spiraled in for its Grand Finale at Saturn.

‘Simply Stunning’

"The image is simply stunning. The image of the Earth evokes the famous 'Blue Marble' image taken by astronaut Harrison Schmitt during Apollo 17...which also showed Africa prominently in the picture." -Noah Petro, Deputy Project Scientist for our Lunar Reconnaissance Orbiter mission.

Goodbye—for now—at 19,000 mph

As part of an engineering test, our OSIRIS-REx spacecraft captured this image of Earth and the Moon in January 2018 from a distance of 39.5 million miles (63.6 million kilometers). When the camera acquired the image, the spacecraft was moving away from our home planet at a speed of 19,000 miles per hour (8.5 kilometers per second). Earth is the largest, brightest spot in the center of the image, with the smaller, dimmer Moon appearing to the right. Several constellations are also visible in the surrounding space.

The View from Mars

A human observer with normal vision, standing on Mars, could easily see Earth and the Moon as two distinct, bright "evening stars."

Moon Photobomb

"This image from the Deep Space Climate Observatory (DSCOVR) satellite captured a unique view of the Moon as it moved in front of the sunlit side of Earth in 2015. It provides a view of the far side of the Moon, which is never directly visible to us here on Earth. “I found this perspective profoundly moving and only through our satellite views could this have been shared.” - Michael Freilich, Director of our Earth Science Division.

Eight Days Out

Eight days after its final encounter with Earth—the second of two gravitational assists from Earth that helped boost the spacecraft to Jupiter—the Galileo spacecraft looked back and captured this remarkable view of our planet and its Moon. The image was taken from a distance of about 3.9 million miles (6.2 million kilometers).

A Slice of Life

Earth from about 393,000 miles (633,000 kilometers) away, as seen by the European Space Agency’s comet-bound Rosetta spacecraft during its third and final swingby of our home planet in 2009.

So Long Earth

The Mercury-bound MESSENGER spacecraft captured several stunning images of Earth during a gravity assist swingby of our home planet on Aug. 2, 2005.

Earth Science: Taking a Closer Look

Our home planet is a beautiful, dynamic place. Our view from Earth orbit sees a planet at change. Check out more images of our beautiful Earth here.

Join Our Earth Day Celebration!

We pioneer and supports an amazing range of advanced technologies and tools to help scientists and environmental specialists better understand and protect our home planet - from space lasers to virtual reality, small satellites and smartphone apps. 

To celebrate Earth Day 2018, April 22, we are highlighting many of these innovative technologies and the amazing applications behind them.

Learn more about our Earth Day plans HERE. 

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From Microscopic to Multicellular: Six Stories of Life that We See from Space

Life. It's the one thing that, so far, makes Earth unique among the thousands of other planets we've discovered. Since the fall of 1997, NASA satellites have continuously and globally observed all plant life at the surface of the land and ocean. During the week of Nov. 13-17, we are sharing stories and videos about how this view of life from space is furthering knowledge of our home planet and the search for life on other worlds.

Earth is the only planet with life, as far as we know. From bacteria in the crevices of the deepest oceans to monkeys swinging between trees, Earth hosts life in all different sizes, shapes and colors. Scientists often study Earth from the ground, but some also look to our satellites to understand how life waxes and wanes on our planet.

Over the years, scientists have used this aerial view to study changes in animal habitats, track disease outbreaks, monitor forests and even help discover a new species. While this list is far from comprehensive, these visual stories of bacteria, plants, land animals, sea creatures and birds show what a view from space can reveal.

1. Monitoring the single-celled powerhouses of the sea

Known as the grass of the ocean, phytoplankton are one of the most abundant types of life in the ocean. Usually single-celled, these plant-like organisms are the base of the marine food chain. They are also responsible for the only long-term transfer of carbon dioxide from Earth’s atmosphere to the ocean. 

Even small changes in phytoplankton populations can affect carbon dioxide concentrations in the atmosphere, which could ultimately affect Earth’s global surface temperatures. Scientists have been observing global phytoplankton populations continuously since 1997 starting with the Sea-Viewing Wide Field-of View Sensor (SeaWiFS). They continue to study the small life-forms by satellite, ships and aircrafts.

2. Predicting cholera bacteria outbreaks

Found on the surface of zooplankton and in contaminated water, the bacteria that cause the infectious disease cholera — Vibrio cholerae — affect millions of people every year with severe diarrhea, sometimes leading to death. While our satellite sensors can’t detect the actual bacteria, scientists use various satellite data to look for the environmental conditions that the bacteria thrive in. 

Specifically, microbiologist Rita Colwell at the University of Maryland, College Park, and West Virginia University hydrologist Antar Jutla studied data showing air and ocean temperature, salinity, precipitation, and chlorophyllconcentrations, the latter a marker for zooplankton. Anticipating where the bacteria will bloom helps researchers to mitigate outbreaks.

Recently, Colwell and Jutla have been able to estimate cholera risk after major events, such as severe storms, by looking at satellite precipitation data, air temperature, and population maps. The two maps above show the team's predicted cholera risk in Haiti two weeks after Hurricane Matthew hit over October 1-2, 2016 and the actual reported cholera cases in October 2016.

3. Viewing life on land

From helping preserve forests for chimpanzees to predicting deer population patterns, scientists use our satellites to study wildlife across the world. Satellites can also see the impacts of perhaps the most relatable animal to us: humans. Every day, we impact our planet in many ways including driving cars, constructing buildings and farming – all of which we can see with satellites.

Our Black Marble image provides a unique view of human activity. Looking at trends in our lights at night, scientists can study how cities develop over time, how lighting and activity changes during certain seasons and holidays, and even aid emergency responders during power outages caused by natural disasters.

4. Tracking bird populations

Scientists use our satellite data to study birds in a variety of ways, from understanding their migratory patterns, to spotting potential nests, to tracking populations. In a rather creative application, scientists used satellite imagery to track Antarctica’s emperor penguin populations by looking for their guano – or excrement.

Counting emperor penguins from the ground perspective is challenging because they breed in some of the most remote and cold places in the world, and in colonies too large to easily count manually. With their black and white coats, emperor penguins are also difficult to count from an aerial view as they sometimes blend in with shadows on the ice. Instead, Phil Trathan and his colleagues at the British Antarctic Survey looked through Landsat imagery for brown stains on the sea ice. By looking for penguin droppings, Trathan said his team identified 54 emperor penguin colonies along the Antarctic coast.

5. Parsing out plant life

Just as we see plants grow and wilt on the ground, satellites observe the changes from space. Flourishing vegetation can indicate a lively ecosystem while changes in greenery can sometimes reveal natural disasters, droughts or even agricultural practices. While satellites can observe plant life in our backyards, scientists can also use them to provide a global picture. 

Using data from satellites including SeaWiFS, and instruments including the NASA/NOAA Visible Infrared Imaging Radiometer Suite and the Moderate Resolution Imaging Spectroradiometer, scientists have the most complete view of global biology to date, covering all of the plant life on land and at the surface of the ocean.

6. Studying life under the sea

Our satellites have helped scientists study creatures living in the oceans whether it’s finding suitable waters for oysters or protecting the endangered blue whale. Scientists also use the data to learn more about one of the most vulnerable ecosystems on the planet – coral reefs.

They may look like rocks or plants on the seafloor, but corals are very much living animals. Receiving sustenance from photosynthetic plankton living within their calcium carbonate structures, coral reefs provide food and shelter for many kinds of marine life, protect shorelines from storms and waves, serve as a source for potential medicines, and operate as some of the most diverse ecosystems on the planet.

However, coral reefs are vulnerable to the warming of the ocean and human activity. Our satellites measure the surface temperature of ocean waters. These measurements have revealed rising water temperatures surrounding coral reef systems around the world, which causes a phenomenon known as “coral bleaching.” To add to the satellite data, scientists use measurements gathered by scuba divers as well as instruments flown on planes.

During the week of Nov. 13-17, check out our stories and videos about how this view of life from space is furthering knowledge of our home planet and the search for life on other worlds. Follow at www.nasa.gov/Earth.

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Solar System: 10 Things to Know This Week

The Living Planet Edition

Whether it's crops, forests or phytoplankton blooms in the ocean, our scientists are tracking life on Earth. Just as satellites help researchers study the atmosphere, rainfall and other physical characteristics of the planet, the ever-improving view from above allows them to study Earth's interconnected life.

1. Life on Earth, From Space

While we (NASA) began monitoring life on land in the 1970s with the Landsat satellites, this fall marks 20 years since we've continuously observed all the plant life at the surface of both the land and ocean. The above animation captures the entirety of two decades of observations.

2. Watching the World Breathe

With the right tools, we can see Earth breathe. With early weather satellite data in the 1970s and '80s, NASA Goddard scientist Compton Tucker was able to see plants' greening and die-back from space. He developed a way of comparing satellite data in two wavelengths.

When healthy plants are stocked with chlorophyll and ready to photosynthesize to make food (and absorb carbon dioxide), leaves absorb red light but reflect infrared light back into space. By comparing the ratio of red to infrared light, Tucker and his colleagues could quantify vegetation covering the land.

Expanding the study to the rest of the globe, the scientists could track rainy and dry seasons in Africa, see the springtime blooms in North America, and wildfires scorching forests worldwide.

3. Like Breathing? Thank Earth's Ocean

But land is only part of the story. The ocean is home to 95 percent of Earth's living space, covering 70 percent of the planet and stretching miles deep. At the base of the ocean's food web is phytoplankton - tiny plants that also undergo photosynthesis to turn nutrients and carbon dioxide into sugar and oxygen. Phytoplankton not only feed the rest of ocean life, they absorb carbon dioxide - and produce about half the oxygen we breathe.

In the Arctic Ocean, an explosion of phytoplankton indicates change. As seasonal sea ice melts, warming waters and more sunlight will trigger a sudden, massive phytoplankton bloom that feeds birds, sea lions and newly-hatched fish. But with warming atmospheric temperatures, that bloom is now happening several weeks earlier - before the animals are in place to take advantage of it.

4. Keeping an Eye on Crops

The "greenness" measurement that scientists use to measure forests and grasslands can also be used to monitor the health of agricultural fields. By the 1980s, food security analysts were approaching NASA to see how satellite images could help with the Famine Early Warning System to identify regions at risk - a partnership that continues today.

With rainfall estimates, vegetation measurements, as well as the recent addition of soil moisture information, our scientists can help organizations like USAID direct emergency help.

The view from space can also help improve agricultural practices. A winery in California, for example, uses individual pixels of Landsat data to determine when to irrigate and how much water to use.

5. Coming Soon to the International Space Station

A laser-based instrument being developed for the International Space Station will provide a unique 3-D view of Earth's forests. The instrument, called GEDI, will be the first to systematically probe the depths of the forests from space.

Another ISS instrument in development, ECOSTRESS, will study how effectively plants use water. That knowledge provided on a global scale from space will tell us "which plants are going to live or die in a future world of greater droughts," said Josh Fisher, a research scientist at NASA's Jet Propulsion Laboratory and science lead for ECOSTRESS.

6. Seeing Life, From the Microscopic to Multicellular

Scientists have used our vantage from space to study changes in animal habitats, track disease outbreaks, monitor forests and even help discover a new species. Bacteria, plants, land animals, sea creatures and birds reveal a changing world.

Our Black Marble image provides a unique view of human activity. Looking at trends in our lights at night, scientists can study how cities develop over time, how lighting and activity changes during certain seasons and holidays, and even aid emergency responders during power outages caused by natural disasters.

7. Earth as Analog and Proving Ground

Just as our Mars rovers were tested in Earth's deserts, the search for life on ocean moons in our solar system is being refined by experiments here. JPL research scientist Morgan Cable looks for life on the moons of Jupiter and Saturn. She cites satellite observations of Arctic and Antarctic ice fields that are informing the planning for a future mission to Europa, an icy moon of Jupiter.

The Earth observations help researchers find ways to date the origin of jumbled, chaotic ice. "When we visit Europa, we want to go to very young places, where material from that ocean is being expressed on the surface," she explained. "Anywhere like that, the chances of finding biomarkers goes up - if they're there."

8. Only One Living Planet

Today, we know of only one living planet: our own. The knowledge and tools NASA developed to study life here are among our greatest assets as we begin the search for life beyond Earth.

There are two main questions: With so many places to look, how can we home in on the places most likely to harbor life? What are the unmistakable signs of life - even if it comes in a form we don't fully understand? In this early phase of the search, "We have to go with the only kind of life we know," said Tony del Genio, co-lead of a new NASA interdisciplinary initiative to search for life on other worlds.

So, the focus is on liquid water. Even bacteria around deep-sea vents that don't need sunlight to live need water. That one necessity rules out many planets that are too close or too far from their stars for water to exist, or too far from us to tell. Our Galileo and Cassini missions revealed that some moons of Jupiter and Saturn are not the dead rocks astronomers had assumed, but appear to have some conditions needed for life beneath icy surfaces.

9. Looking for Life Beyond Our Solar System

In the exoplanet (planets outside our solar system that orbit another star) world, it's possible to calculate the range of distances for any star where orbiting planets could have liquid water. This is called the star's habitable zone. Astronomers have already located some habitable-zone planets, and research scientist Andrew Rushby of NASA Ames Research Center is researching ways to refine the search. "An alien would spot three planets in our solar system in the habitable zone [Earth, Mars and Venus]," Rushby said, "but we know that 67 percent of those planets are not inhabited."

He recently developed a model of Earth's carbon cycle and combined it with other tools to study which planets in habitable zones would be the best targets to look for life, considering probable tectonic activity and water cycles. He found that larger planets are more likely than smaller ones to have surface temperatures conducive to liquid water. Other exoplanet researchers are looking for rocky worlds, and biosignatures, the chemical signs of life.

10. You Can Learn a Lot from a Dot

When humans start collecting direct images of exoplanets, even the closest ones will appear as only a handful of pixels in the detector - something like the famous "blue dot" image of Earth from Saturn. What can we learn about life on these planets from a single dot?

Stephen Kane of the University of California, Riverside, has come up with a way to answer that question by using our EPIC camera on NOAA's DSCOVR satellite. "I'm taking these glorious pictures and collapsing them down to a single pixel or handful of pixels," Kane explained. He runs the light through a noise filter that attempts to simulate the interference expected from an exoplanet mission. By observing how the brightness of Earth changes when mostly land is in view compared with mostly water, Kane reverse-engineers Earth's rotation rate - something that has yet to be measured directly for exoplanets.

The most universal, most profound question about any unknown world is whether it harbors life. The quest to find life beyond Earth is just beginning, but it will be informed by the study of our own living planet.

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Our pale blue dot, planet Earth, is seen in this video captured by NASA astronaut Jack Fischer from his unique vantage point on the International Space Station. From 250 miles above our home planet, this time-lapse imagery takes us over the Pacific Ocean’s moon glint and above the night lights of San Francisco, CA. The thin hue of our atmosphere is visible surrounding our planet with a majestic white layer of clouds sporadically seen underneath.

The International Space Station is currently home to 6 people who are living and working in microgravity. As it orbits our planet at 17,500 miles per hour, the crew onboard is conducting important research that benefits life here on Earth.

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