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Earth Day — 50th Anniversary in April 2020

Space Agencies honour Earth Day     NASA recollections and perspectives on Earth Day
ESA is taking the pulse of Earth    References

Earth Day is an annual event celebrated around the world on April 22 to demonstrate support for environmental protection. First celebrated in 1970, it now includes events coordinated globally by the Earth Day Network in more than 193 countries. 1)

Earth Day was first observed on April 22, 1970, when an estimated 20 million people nationwide attended the inaugural events at tens of thousands of sites including elementary and secondary schools, universities, and community sites across the United States. Earth Day 1970 gave a voice to an emerging public consciousness about the state of our planet.

In the decades leading up to the first Earth Day, Americans were consuming vast amounts of leaded gas through massive and inefficient automobiles. Industry belched out smoke and sludge with little fear of the consequences from either the law or bad press. Air pollution was commonly accepted as the smell of prosperity. Until this point, mainstream America remained largely oblivious to environmental concerns and how a polluted environment threatens human health.

However, the stage was set for change with the publication of Rachel Carson’s New York Times bestseller ”Silent Spring” in 1962. The book represented a watershed moment, selling more than 500,000 copies in 24 countries as it raised public awareness and concern for living organisms, the environment and the inextricable links between pollution and public health.

Earth Day 1970 would come to provide a voice to this emerging environmental consciousness, and putting environmental concerns on the front page.

The idea for the first Earth Day: Senator Gaylord Nelson, a junior senator from Wisconsin, had long been concerned about the deteriorating environment in the United States. Then in January 1969, he and many others witnessed the ravages of a massive oil spill in Santa Barbara, California. Inspired by the student anti-war movement, Senator Nelson wanted to infuse the energy of student anti-war protests with an emerging public consciousness about air and water pollution. Senator Nelson announced the idea for a teach-in on college campuses to the national media, and persuaded Pete McCloskey, a conservation-minded Republican Congressman, to serve as his co-chair. They recruited Denis Hayes, a young activist, to organize the campus teach-ins and they choose April 22, a weekday falling between Spring Break and Final Exams, to maximize the greatest student participation.

Earth Day 1970 achieved a rare political alignment, enlisting support from Republicans and Democrats, rich and poor, urban dwellers and farmers, business and labor leaders. By the end of 1970, the first Earth Day led to the creation of the United States Environmental Protection Agency (EPA) and the passage of other first of their kind environmental laws, including the National Environmental Education Act, the Occupational Safety and Health Act, and the Clean Air Act.

1990: EARTH DAY GOES GLOBAL:

As 1990 approached, a group of environmental leaders approached Denis Hayes to once again organize another major campaign for the planet. This time, Earth Day went global, mobilizing 200 million people in 141 countries and lifting environmental issues onto the world stage. Earth Day 1990 gave a huge boost to recycling efforts worldwide and helped pave the way for the 1992 United Nations Earth Summit in Rio de Janeiro. It also prompted President Bill Clinton to award Senator Nelson the Presidential Medal of Freedom — the highest honor given to civilians in the United States — for his role as Earth Day founder.

EARTH DAY TODAY:

Today, Earth Day is widely recognized as the largest secular observance in the world, marked by more than a billion people every year as a day of action to change human behavior and create global, national and local policy changes.

Now, the fight for a clean environment continues with increasing urgency, as the ravages of climate change become more and more apparent every day.

As the awareness of our climate crisis grows, so does civil society mobilization, which is reaching a fever pitch across the globe today. Disillusioned by the low level of ambition following the adoption of the Paris Agreement in 2015 and frustrated with international environmental lethargy, citizens of the world are rising up to demand far greater action for our planet and its people.

Earth Day sparked a wave of international action. In 2016, the United Nations chose this very day – 22 April – as the day when the landmark Paris Agreement was signed. Recognized as International Mother Earth Day by the United Nations, today reflects a day committed to understanding our planet’s health – protecting it for future generations to come.

The scientific evidence of global climate change is irrefutable. International organisations, such as the IPCC (Intergovernmental Panel on Climate Change), have warned of the consequences of a warming climate – affecting fresh water resources, global food production, sea level and triggering an increase in extreme-weather events.

The social and cultural environments we saw in 1970 are rising up again today — a fresh and frustrated generation of young people are refusing to settle for platitudes, instead taking to the streets by the millions to demand a new way forward. Digital and social media are bringing these conversations, protests, strikes and mobilizations to a global audience, uniting a concerned citizenry as never before and catalyzing generations to join together to take on the greatest challenge that humankind has faced.

By tapping into some of the learnings, outcomes, and legacy of the first Earth Day, Earth Day Network (EDN) is building a cohesive, coordinated, diverse movement, one that goes to the very heart of what EDN and Earth Day are all about — empowering individuals with the information, the tools, the messaging and the communities needed to make an impact and drive change.

Table 1: Some background on the origins of Earth Day

On Earth Day, April 22, 2020, we have two crises: One is the COVID-19 coronavirus pandemic. The other is a slowly building disaster for our climate. We can, will and must solve both challenges. The world was not prepared for the novel coronavirus. But we still have time to prepare — in every part of the world — for the climate crisis. 2)




Space Agencies honor Earth Day

To honor the day's 50th anniversary, NASA's JPL has unveiled posters in which our home planet is the star. 3)

When Apollo 8 astronaut William Anders snapped the iconic Earthrise image, it captured the imagination of the people on Earth and helped to inspire the first Earth Day, on April 22, 1970. In the image, our planet hangs at a gibbous phase, as a far-off world rising in the night sky, and reminds us of the fragility of our home.

"We came all this way to explore the Moon, and the most important thing is that we discovered the Earth," was how Anders summed up the astonishing sight.

In honor of Earth Day, NASA's Jet Propulsion Laboratory has created downloadable posters that celebrate this remarkable planet.

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Figure 1: Earthrise by Apollo 8 astronaut William Anders, December 1968. Earth at gibbous phase as seen from the Moon (image credit: NASA)

Earth Phases

Humanity has spent millennia studying the Moon and depicting its phases, but people often don't realize that Earth has phases, too.

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Figure 2: Our planet's phases wax and wane - just as the Moon's phases do - but in reverse order. Unlike the Moon, which always shows the same face to Earth, our planet spins noticeably on its axis every day. So someone on the Moon looking at Earth would observe its surface features change each day, as well as its phase. Shifting the perspective between planets and their moons, this poster captures those phases as they would be seen from the Moon, including the full Earth as it will actually appear on April 22, 2020 (image credit: NASA/JPL Caltech)




NASA recollections and future perspectives on Earth Day 2020

In 1970, the United States Clean Air Act underwent major revisions to reduce pollution and protect air quality, President Nixon created the Environmental Protection Agency, and NASA scientists were cracking open the door on a new era of studying our home planet from space. 4)

The first black-and-white satellite images of Earth were just ten years old: a swirling mass of white clouds over back oceans. The first measurements of Earth’s temperature from space were made just a year prior in 1969 by Nimbus 3, a joint mission with the National Oceanic and Atmospheric Administration, which became a major step in improving weather forecasts.

NASA scientists and engineers, in partnership with the U.S. Geological Survey, were two years away from launching the first Landsat satellite in 1972, beginning a now-48-year continuous record of Earth’s land surfaces that have shown dramatic changes in forests, farming, water use, and cities over time. International scientists were 15 years away from observing proof of significant damage to the upper atmosphere ozone layer that protects life on Earth from harmful ultraviolet radiation. The 1985 Antarctic ozone hole was confirmed by data from NASA satellites and led to the 1987 Montreal Protocol, the most successful international environmental intervention to date.

In the 50 years since the first Earth Day, the view from space has revolutionized our understanding of Earth’s interconnected atmosphere, oceans, freshwater, ice, land, ecosystems, and climate. NASA has been at the forefront of innovation, both of the technology capable of observing properties of the Earth and in the research and researchers that take those observations and combine them with ground data and computing power to create a more holistic picture of our changing planet. Then, NASA takes one more step to get our satellite data and research into the hands of people working on the ground to solve problems and meet environmental challenges facing their communities, today and for the future.

Looking ahead at the next 50 years, we've asked researchers across the agency about the big questions in their fields and the role they see NASA playing to meet those challenges, from crop and water management to disaster preparedness and pollution reduction. We’ve shared them here in their own words.

Figure 3: In the 50 years since the first Earth Day, the view from space has revolutionized our understanding of Earth’s interconnected atmosphere, oceans, freshwater, ice, land, ecosystems, and climate. Looking ahead at the next 50 years, we've asked researchers across the agency about the big questions in their fields and the role they see NASA playing to meet environmental challenges (image credit: NASA)

Figure 4: Earth Day 2020: NASA Puts Space to Work for the Planet. NASA’s unique vantage point of space allows us to better understand Earth’s interconnected systems and use that knowledge to live sustainably on our home planet, protect life around the world, and adapt to natural and human-caused changes. As NASA joins the world in observing the 50th anniversary of Earth Day, we reaffirm our commitment to understanding our planet’s interconnected systems to help protect them for future generations (video credit: NASA) 5)


Some examples of Projects and their Leaders

1) Gioia Massa, the lead of NASA's Veggie project at KSC (Kennedy Space Center)

I work in the area of space crop production and currently our focus is looking at supplementing the astronauts’ packaged diet with fresh produce that can be grown on the International Space Station and on longer duration missions later on. The lettuce crops that we grew in the Veggie Chamber were very similar between space and ground in terms of their nutrition and their microbiology. Plants are going to be critical for human exploration and especially as we go on to Mars. We’re going to have to become more self-sustainable and be able to produce a larger percentage of our food the more that we colonize space.

A lot of things have spun off from research for space crop production, which are now very important for Earth-based agriculture. We’re learning a lot from the people that are developing controlled environment farming systems indoors, usually in big cities to help provide fresh produce, and we are translating a lot of our space research back to them. In the future I think we’ll see more research on making plant growth systems more sustainable, for example, being able to recycle all of the inedible plant material. Things that we might think of as wastes, we have to think of as resources. Another area where I see changes coming is understanding the microbiome of the crop, where we really understand how plants, humans, and the microbiology interact, and then learn how to use this microbiome to protect plants and food.

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Figure 5: Gioia Massa is the NASA Veggie project lead at NASA’s Kennedy Space Center, working with astronauts on the International Space Station to grow plants in space. She’s a 2019 recipient of the Presidential Early Career Award for Scientists and Engineers (image credit: NASA)

2) JT Teager in the terrestrial hydrology group at NASA/JPL (Jet Propulsion Laboratory)

As Earth Scientists, we're kind of like doctors for the planet. Just like a doctor listens to your heart with a stethoscope or takes your temperature with a thermometer, we have different instruments in space that are taking the vital signs of the planet. My specialty is water. I use a couple of satellites, particularly the Gravity Recovery and Climate Experiment (GRACE) satellites, which are a partnership between NASA and the German Research Centre for Geosciences, to study the movement of water and how wet and dry the climate is at different times. The satellites measure changes to Earth's gravity field. Since water is typically the only thing heavy enough and that moves fast enough to cause changes in gravity on a regular basis, the gravity data tells us a lot. We're able use it to better understand how water moves – hydrological extremes like floods and drought, changing water resources, and how much water we might have in the future with things like climate change and a growing population.

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Figure 6: JT Reager is a scientist in the terrestrial hydrology group at NASA's Jet Propulsion Laboratory. He is a 2019 recipient of the Presidential Early Career Award for Scientists and Engineers for his groundbreaking analysis of the way water moves around the globe (image credit: NASA)

Right now, we have more information on the state of the planet coming in than we've had at any point in our history. So it's not more data that I worry about. But in the next 20 to 50 years, I hope to see a shift in terms of collectively having more respect for nature and the resources it provides, and living in better harmony with our planet.

3) Jeanne Holm is the Deputy Chief Information Officer and the Senior Tech Advisor for the City of Los Angeles

NASA doesn’t just produce amazing pictures. These satellite images can tell us if our efforts to reduce air pollution on Earth are making a perceptible difference from space. The air we breathe affects our quality of life and longevity. By planting more trees and regulating automobiles and gasoline production, we can improve air quality around the world. To that end, I am working on a project that will use artificial intelligence and machine learning to examine and mine NASA satellite and on-the-ground sensor data to show the impact of our pollution mitigation efforts.

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Figure 7: Jeanne recently won funding from NASA’s Advanced Information Systems Technology program to create a new platform to monitor and improve air quality across the planet (image credit: Jeanne Holm)

By 2030, the City of Los Angeles hopes to see some neighborhoods vastly improve their air quality and achieve a zero fossil fuel footprint. To do this, we’ll need to improve how we construct new buildings, retrofit existing buildings and build transportation infrastructure to allow for more public transit and autonomous electric vehicles. We’ll also need to think about ways we can realistically and sustainably change human behavior. Younger generations want to do things differently; we can empower them to do just that.

4) Rich Moore is an airborne atmospheric scientist at NASA’s Langley Research Center

Space is a great vantage point to view the Earth and how it changes over days, months and years — but the satellites are so far away. Imagine peering through a powerful camera that’s hundreds of miles away and trying to decipher the image. Some of the small details are bound to get lost, so we use airplanes, balloons and UAVs to get a closer look at what’s going on in the atmosphere.

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Figure 8: Richard Moore is a 2019 recipient of the Presidential Early Career Award for Scientists and Engineers for innovative contributions to aerosol-cloud-climate interactions ( image credit: NASA)

In the future, we want to really understand what the air quality looks like at "nose-level," where people are living and breathing. New geostationary satellites — one that was launched by South Korea (KOMPSAT-2B) this year and two that will launch in coming years, one from the U.S. (TEMPO) and one from Europe (Sentinel-5P) — will measure air pollution every hour over specific regions of the world using passive remote sensors called spectrometers, which make measurements from reflected light. This will be transformative in how we track the movement of pollution in the coming decades.

Critical for giving us improved vertical views of Earth's atmosphere will be active remote sensors such as radars, which use radio waves to make measurements, and lidars, which use lasers. Future versions of these instruments could be particularly useful in cloudy areas of the world where passive satellite imagers struggle to distinguish between particles in clear air and cloud droplets. It’s hard to draw a sharp line on where a cloud begins and ends, and some people have termed the transition region from clear to cloudy sky as the "twilight zone." High resolution vertical data from these active sensors holds especially great promise in these regions.


Down to Earth

NASA astronaut Jessica Meir rocks her CAVES shirt on board the International Space Station. Jessica was the first woman to participate in ESA’s underground astronaut training program in 2016. 6)

It might not be obvious, but there are many similarities between working deep underground and in outer space.

Since 2011, ESA’s CAVES (Cooperative Adventure for Valuing and Exercising human behavior and performance Skills) course has been taking astronauts below Earth’s surface and preparing them to work safely and effectively as representative spaceflight teams in an environment where risk, scientific operations and living conditions have many similarities to space . At the end of the course astronauts are better prepared to participate in long term ISS expeditions, balancing mission goals, environmental risks, team demands through their individual skills and team processes.

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Figure 9: NASA astronaut Jessica Meir rocks her CAVES shirt in the Cupola on the International Space Station (image credit: NASA)

As many as 34 astronauts from six agencies have scouted caves to experience the challenges and excitement of exploring alien environments on Earth.

Jessica joined the 2016 edition along with five astronauts from China, Japan, USA, Spain and Russia in the caves of Sardinia, Italy, to explore the depths and train for life in outer space. As the team’s biologist, Jessica was tasked with searching for alien underground life. Jessica talked about her love for exploration and her experience at CAVES in her video before launching to the Space Station.

Just as with spacewalks, the underground ‘cavewalks’ required safety tethering, 3D orientation, careful planning and teamwork. Jessica and her fellow cave explorers needed to stay alert in an environment where they were deprived of natural light and every move was a step into the unknown.

The experience no doubt complemented the extensive spacewalk training she has since received. Jessica went on to conduct the first ever all-female spacewalk during her 205 days in space. Alongside NASA astronaut and friend Christina Koch, the women totalled 21 hours and 44 minutes outside the Space Station across three historic spacewalks.

The next ESA Caves course will take place in 2021. ESA astronaut Samantha Cristoforetti is tentatively booked for the course. Follow all the Caves adventures on the blog.

From under the Earth to above it, Jessica is now back down on our planet. She returned with fellow NASA astronaut Drew Morgan and cosmonaut Oleg Skripochka on 17 April 2020.

Given a global pandemic and strict quarantine measures, the crew were welcomed home, just in time for Earth Day on 22 April. The annual event to mark environmental protection is celebrating its 50th anniversary and is the first to be celebrated from home.

As difficult as quarantine has been for communities across the globe, the impact on our planet is noticeable. Analyses from Earth observation satellites are showing the continued low levels of nitrogen dioxide concentrations across Europe – coinciding with lockdown measures implemented to stop the spread of the coronavirus.

In light of this, staying home does not seem such a bad way to celebrate Earth Day.




ESA is taking the pulse of Earth

For Earth-observing satellites, every day is Earth Day. While news of COVID-19 (Corona Virus Disease-19) dominates headlines and many of us practice social distancing, there still remains the need for action on climate change – and satellites are vital in providing the key facts on this global issue. 7)

In order to tackle climate change, scientists and governments need reliable data in order to understand how our planet is changing. For more than 30 years, Earth observation satellites have gathered valuable data to meet the challenges of our world.

Figure 10: We are all facing the consequences of a rapidly changing world, but thanks to the satellite era we are better placed to understand the complexities of our planet, particularly with respect to global change. Today’s satellites are used to forecast the weather, answer important Earth-science questions, provide essential information to improve agricultural practices, maritime safety, help when disaster strikes, and all manner of everyday applications. — The need for information from satellites is growing at an ever-increasing rate. ESA (European Space Agency) is a world-leader in Earth observation and remains dedicated to developing cutting-edge spaceborne technology to further understand the planet, improve daily lives, support effect policy-making for a more sustainable future, and benefit businesses and the economy (video credit: ESA)

Satellites provide unequivocal evidence of the changes taking place on Earth and provide the big picture, collecting long-term series of data, in order to understand its effects. ESA and their partners have recently tracked rapidly melting ice in Greenland and Antarctica, discovered unusual ozone holes, mapped wildfires from space and monitored air pollution in our atmosphere.

With four EU Copernicus Sentinel missions and four Earth Explorer missions in orbit, the satellites cover a vast array of areas, such as ice thickness coverage, deforestation, soil moisture, sea level and ocean surface temperature, as well as other essential climate variables.

The observations provide us with a global coverage, revisiting the same region every few days and proving a good understanding of the health and behavior of our planet – and how it is affected by climate change. Through ESA’s Climate Change Initiative, long-term datasets on key indicators of climate change are being systematically generated and preserved.

ESA’s Director of Earth Observation Programs, Josef Aschbacher, says, “Earth observation has changed the way we comprehend our profound impact on the environment. Thanks to these sophisticated missions, we have an abundance of data that allows us to take the pulse of our planet.

“ESA is ready to deliver the hard facts required to tackle and address important environmental issues. For us in It is important we take some time today – Earth Day – to appreciate the beauty of our planet and learn more about the impact we have on our changing climate.”

There are many ways to actively participate in Earth Day 2020 online. Join the Earth Day live discussion, learn more about what ESA does to combat climate change or explore our gallery of selected images from space.

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Figure 11: ESA has been dedicated to observing Earth from space ever since the launch of its first Meteosat weather satellite back in 1977. With the launch of a range of different types of satellites over the last 40 years, we are better placed to understand the complexities of our planet, particularly with respect to global change. Today’s satellites are used to forecast the weather, answer important Earth-science questions, provide essential information to improve agricultural practices, maritime safety, help when disaster strikes, and all manner of everyday applications. - The need for information from satellites is growing at an ever-increasing rate. With ESA as world-leader in Earth observation, the Agency remains dedicated to developing cutting-edge spaceborne technology to further understand the planet, improve daily lives and support effect policy-making for a more sustainable future (image credit: ESA, CC BY-SA 3.0 IGO)

Figure 12: “It can be done.” - an Earth Day message. In summer 2018, ESA joined with the musician Vangelis and the family of scientist Prof. Stephen Hawking to beam a message marking his passing to the nearest black hole. On 22 April 2020, Earth Day, we're transmitting this poignant message to all of planet Earth - as a message of hope, to say that, by working together, we can overcome this crisis and others facing humankind [Text and narration of the video: Prof. Stephen Hawking, (© The Estate of Stephen Hawking), Music: The Stephen Hawking Tribute by Vangelis (composed, arranged, produced and performed by Vangelis) 2018] 8)

The message of Stephen Hawking reads: “I am very aware of the preciousness of time. Seize the moment. Act now.

“I have spent my life travelling across the Universe inside my mind. Through theoretical physics I have sought to answer some of the great questions but there are other challenges, other big questions which must be answered, and these will also need a new generation who are interested, engaged and with an understanding of science.

“How will we feed an ever-growing population, provide clean water, generate renewable energy, prevent and cure disease and slow down global climate change?

“I hope that science and technology will provide the answers to these questions, but it will take people, human beings with knowledge and understanding to implement the solution.

“One of the great revelations of the space age has been a perspective that has given humanity on ourselves. When we see the Earth from space we see ourselves as a whole; we see the unity and not the divisions. It is such a simple image, with a compelling message: one planet, one human race.

“We are here together, and we need to live together with tolerance and respect. We must become global citizens.

“I have been enormously privileged through my work to be able to contribute to our understanding of the Universe. But it would be an empty Universe indeed, if it were not for the people I love and who love me.

“We are all time travellers journeying together into the future. But let us work together to make that future a place we want to visit. Be brave, be determined, overcome the odds. It can be done.”




Nine Reasons We’re Grateful to Live on Earth

• April 21, 2020: Earth can sometimes feel like the last place you’d want to be. Indeed, a number of explorers have devised inventive ways to move civilization off this planet. 9)

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Figure 13: Expedition 48 Commander Jeff Williams of NASA shared this sunrise panorama taken from his vantage point aboard the International Space Station, writing, "Morning over the Atlantic ... this one will hang on my wall."This image was published in August 2017 (image credit: NASA)

- It’s no surprise: The promise of a better life in the mysterious beyond can be seductive. But the fact is the more we learn about out there the more we realize how special it is here. The first astronauts to look from space back at Earth, a “pale blue dot, the only home we've ever known,” as scientist Carl Sagan once wrote, saw a beautiful, delicate world that is perfectly suited to the bounty of life it supports.

- “When I looked up and saw the Earth coming up on this very stark, beat up lunar horizon, an Earth that was the only color that we could see, a very fragile looking Earth, a very delicate looking Earth, I was immediately almost overcome by the thought that here we came all this way to the Moon, and yet the most significant thing we’re seeing is our own home planet, the Earth,” said William Anders, a crew member on Apollo 8, the first crewed mission to the Moon.

- On this 50th anniversary of Earth Day on April 22, we reflect on nine reasons Earth is the best place to live:

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Figure 14: This mosaic was assembled in 2018 from dozens of images taken by the Mast Camera (Mastcam) on NASA's Curiosity rover. In the image, you're looking uphill at Mount Sharp, which is in the middle of Gale Crater on Mars. The scene has been white-balanced so the colors of the rock materials resemble how they would appear under daytime lighting conditions on Earth (image credit: NASA/JPL-Caltech/MSSS)

1) We can take deep, cleansing breaths

Known as the Red Planet because of the rust particles in its soil that give it a reddish hue, Mars has always fascinated the human mind. What would it be like to live on this not-so-distant world, many have wondered? One day, astronauts will find out. But we know already that living there would require some major adjustments. No longer would we be able to take long, deep breaths of nitrogen- and oxygen-rich air while a gentle spring breeze grazes the skin. Without a spacesuit providing essential life support, humans would have to inhale carbon dioxide, a toxic gas we typically exhale as a waste product. On top of that, the thin Martian atmosphere (100 times thinner than Earth’s) and lack of a global magnetic field would leave us vulnerable to harmful radiation that damages cells and DNA; the low gravity (38% of Earth’s) would weaken our bones. Besides the hardships our bodies would endure, it would simply be less fun to live on Mars. Summer trips to the beach? Forget them. On Mars, there’s plenty of sand, but not a single swimming hole, much less a lake or ocean, and the average temperature is around minus 81 degrees Fahrenheit (minus 63 degrees Celsius). Even the hardiest humans would find the Martian climate to be a drag. —Staci Tiedeken, planetary science outreach coordinator, NASA’s Goddard Space Flight Center.

Figure 15: One minute video of NASA's SDO (Solar Dynamics Observatory) showing the two solar X flares on September 6, 2017. The second was an X9.3 flare — the largest of the solar cycle (video credit: NASA/GSFC)

2) There’s solid ground to stand on

Earth has grassy fields, rugged mountains and icy glaciers. But to live on the Sun, we’d have to kiss all solid ground goodbye. The Sun is a giant ball of plasma, or super-heated gas. If you tried to stand on the Sun’s visible surface, called the photosphere, you’d fall right through, about 205,000 miles (330,000 kilometers) until you reached a layer of plasma so compressed, it’s as thick as water. But you wouldn’t float, because you’d be crushed by the pressure there: 4.5 million times stronger than the deepest point in the ocean. Get ready for a quick descent, too. The Sun’s gravity is 28 times stronger than Earth’s. Thus, a 170-pound (77 kg) adult on Earth would weigh an extra 4,590 pounds (2,245 kg) at the Sun. That would feel like wearing an SUV on your back! If a person managed to hover in the photosphere, though, it might get a little warm. The temperature there is around 10,000 º F (5,500º C), about five to 10 times hotter than lava — yet, not nearly the hottest temperature on the Sun. Don’t worry, though, there would be a break of 3,000 º F (1,600º C) if you stumbled on a sunspot, which is a “cool” region formed by intense magnetic fields. These conditions would have even the most intrepid adventurers longing for the comforts of home. —Miles Hatfield, science writer, NASA's Goddard Space Flight Center.

Figure 16: By studying planet Venus, scientists could learn a great deal about exoplanets, as well as the past, present, and possible future of our own planet. Watch this video to learn more! Our galaxy contains billions of other planets, but we know very little about them. If we had the chance to study one of these exoplanets in greater detail, and could find one with similar characteristics as Earth, scientists could learn a great deal more about planetary evolution and habitability. Surprisingly, there is a nearby planet we could study right now in greater depth that would not only teach us about our planet, but also about many exoplanets. This planet is our neighbor Venus, and this video unveils details on this mysterious nearby world, and serves as a call to action to explore its many features. Venus-like exoplanets may represent one of the most common and observable types of worlds, and the history of Venus may be the key to understanding the evolution of habitability as a planetary process (video credit: NASA/GSFC)

3) The seasons go round and round

Since the beginning of recorded history, people have tracked and celebrated nature’s transition from the desolate days of winter, to the brilliant radiance of spring, to the endless days of summer, and so on. Seasons come from a planet’s tilt on its axis (Earth’s is 23.5 degrees), which tips each hemisphere either toward or away from the heat of the Sun throughout the year. Venus, barely tilted on its axis, has no seasons, though there are hints that it may have once looked and behaved much like Earth, including having oceans covering its rocky surface. But these days, our neighboring planet has an atmosphere so thick (55 times denser than Earth’s) it helps keep Venus at a searing 900 º F (465º C) year round — that’s hotter than the hottest home oven. This oppressive atmosphere also blots out the sky, making it impossible to stargaze from the surface. But Venus isn’t all bad. Despite the low quality of life, there is one benefit of living there: The Venusian year (225 Earth days) is shorter than its day (243 Earth days). That means you can celebrate your birthday every day on Venus! —Lonnie Shekhtman, science writer, NASA's Goddard Space Flight Center

Figure 17: This artist’s rendering illustrates a star getting shredded by a black hole. When a star wanders too close to a black hole, intense tidal forces rip the star apart. In these events, called “tidal disruptions,” some of the stellar debris is flung outward at high speed while the rest falls toward the black hole. This causes a distinct X-ray flare that can last for a few years. NASA’s Chandra X-ray Observatory, Swift Gamma-ray Burst Explorer, and ESA/NASA’s XMM-Newton collected different pieces of this astronomical puzzle in a tidal disruption event called ASASSN-14li, which was found in an optical search by the All-Sky Automated Survey for Supernovae (ASAS-SN) in November 2014 (video credit: NASA/GSFC)

4) Its gravity doesn’t turn us into noodles

Capturing the imaginations of scientists and sci-fi writers alike, black holes are extremely compact objects that do not let any light escape. The surface of a black hole is an area called the “event horizon,” a boundary beyond which nothing can ever return. Even if we were fortunate enough to have a spaceship that could travel to a relatively nearby black hole, its gravity is so strong that approaching too close would stretch and compress the spacecraft and everyone inside it into a noodle shape — a fate scientists call “spaghettification.” Making matters even weirder, time ticks by more slowly around a black hole. To someone watching from far away as a spaceship fell into the event horizon, the vehicle would appear to slow down more the closer it got — and never quite get there. Fortunately, there are no known black holes in the vicinity of Earth or anywhere in the solar system, so we’re safe for now. And we’re lucky that Earth has just the right amount of gravity — enough so we don’t go flying away, but not so much that we can’t stand up and run around. If you still think traveling to a black hole would be a good idea, check out this black hole safety video. —Elizabeth Landau, writer, NASA Headquarters.

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Figure 18: An image of Jupiter (image credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill)

5) We can enjoy a pleasant breeze

Jupiter’s breathtaking swirls of colorful cloud bands might make this planet an appealing vacation destination ... for skydivers. They’d need to bring along their own oxygen, since Jupiter’s atmosphere is made mostly of hydrogen and helium (same as our Sun), with clouds of mostly ammonia. Descending through Jupiter’s clouds is for the most extreme thrill seekers. Given the planet’s strong gravity and super-fast rotation on its axis compared to Earth (10 hours vs. 24 hours), a skydiver would tumble 2.5 times faster than they would on Earth, while getting knocked around by winds raging between 270 and 425 miles per hour (430 to 680 km/hr). Jupiter’s winds make Earth’s highest category hurricane feel like a breeze, and its lightning strikes are up to 1,000 times more powerful than ours. Even if a skydiver does make it through the hundreds of miles, or kilometers, of atmosphere, plus crushing air pressure and extreme heat, it’s not clear they’ll reach a solid surface. Scientist don’t know yet whether Jupiter, a giant planet that can fit 1,300 Earths inside of it, has a solid core. Having solid ground to stand is starting to sound like a luxury. —Staci Tiedeken, planetary science outreach coordinator, NASA’s Goddard Space Flight Center.

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Figure 19: Jupiter's moon Io, the most volcanic body in the solar system, is seen in this 1997 image taken by NASA's Galileo spacecraft (image credit: NASA/JPL/University of Arizona)

6) It’s a sparkling globe of blue, white and green

In places where ocean tides are highest on Earth, the difference between low and high tide is about 50 feet (15 meters). Compare that to Io. This moon of Jupiter is caught in a tug-of-war between the planet’s massive gravity and the pulling of two neighboring moons, Europa and Ganymede. These forces cause Io's surface to regularly bulge up and down by as much as 330 feet (100 meters) — and we’re talking about rock, not water. All this motion has consequences: Io’s interior is very hot, making this moon the most volcanically active world in the solar system. Io, which from space looks like a moldy cheese pizza, has hundreds of volcanoes. Some erupt lava fountains dozens of miles (or kilometers) high. Between all the lava, a thin sulfur dioxide atmosphere and intense radiation from nearby Jupiter, Io doesn’t offer much of a beach vacation for humans. —Bill Dunford, writer and web producer, NASA's Jet Propulsion Laboratory.

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Figure 20: This artist's concept of a lake at the north pole of Saturn's moon Titan illustrates raised rims and rampartlike features such as those seen by NASA's Cassini spacecraft around the moon's Winnipeg Lacus. New research using Cassini radar data and modeling proposes that lake basins like these are likely explosion craters, which could have formed when liquid molecular nitrogen deposits within the crust warmed and quickly turned to vapor, blowing holes in the moon's crust. This would have happened during a warming event (or events) that occurred in a colder, nitrogen-dominated period in Titan's past. The new research may provide evidence of these cold periods in Titan's past, followed by a relative warming to conditions like those of today. Although Titan is frigid compared to Earth, methane in the atmosphere provides a greenhouse effect that warms the moon's surface (image credit: NASA/JPL-Caltech)

7) It’s got clear skies, sunny days and water we can swim in

If there is one place in the universe we know of that could compete with Earth as a home for humans, Titan is it. This satellite of Saturn is the second largest moon in our solar system after Ganymede. Titan is in some ways the most similar world to ours that we have found. Its thick atmosphere would remind us of home, though the air pressure there is slightly higher than Earth's. The atmosphere would defend humans against harmful radiation. Like Earth, Titan also has clouds, rain, lakes and rivers, and even a subsurface ocean of salty water. Even the moon’s terrain and landscape look eerily similar to some parts of Earth. While Titan sounds promising, it has major flaws. Chief among them is oxygen — there isn’t any in the atmosphere. And those lovely rivers and lakes? They’re made of liquid methane. So don’t pack your bathing suit just yet; our bodies are denser than the methane, so they’d sink like boulders. Another thing you’d miss on Titan is seeing the Sun above your head, dazzling against an azure sky. Not only is Titan much farther from the Sun than is Earth, its hazy atmosphere dims the sunlight, making daytime appear like twilight on Earth. —Lonnie Shekhtman, science writer, NASA's Goddard Space Flight Center.

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Figure 21: Made from images taken by NASA's Galileo spacecraft in the late 1990s, this processed color view is one of the best images Earthlings have of Jupiter’s moon Europa. This little moon may be the best place in our solar system to look for life beyond Earth (image credit: NASA/JPL-Caltech/SETI Institute)

8) Dry land exists! And the entire world isn’t smothered beneath miles of ice

Jupiter’s moon Europa is one of the best places to search for life beyond Earth. It may harbor more liquid water than all of Earth’s oceans combined. Just picture yourself standing on a warm, sandy beach, admiring the sunlight glimmering on an ocean that reaches from horizon to horizon. And then prepare to be disappointed. Europa’s ocean is global. It has no beach. No shore. Only ocean, all the way around. Sunlight doesn’t glimmer on the water and there are no waves because Europa’s ocean is hidden beneath miles — perhaps tens of miles — of ice that encases the entire moon. Europa is also tidally locked, meaning if a person stood on its Jupiter-facing side (like our Moon, one hemisphere always faces its parent planet), the solar system’s largest planet would loom overhead and never set. A sublime setting for a romantic stroll? No. Europa has a practically nonexistent atmosphere and brutally cold temperatures ranging from about minus 210 to minus 370º F (minus 134 to minus 223º C). A spacesuit might help with the temperature and pressure, but it can’t protect against those pesky atomic particles captured in Jupiter’s magnetic field, endlessly lashing Europa with such energy that they can blast apart molecules and ionize atoms. Europa’s ionizing radiation would damage or destroy cells in the human body, leading to radiation sickness. —Jay R. Thompson, writer, NASA's Jet Propulsion Laboratory.

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Figure 22: Kepler-7b (right), which is 1.5 times the radius of Jupiter (left), is the first exoplanet to have its clouds mapped. The cloud map was produced using data from NASA's Kepler and Spitzer space telescopes (image credit: NASA/JPL)

9) Cream puff clouds that come and go

With more than 4,000 planets discovered so far outside our solar system, called “exoplanets,” we don’t know of any that offers the comforts of Earthly living — and many would be downright nightmares. Take Kepler-7b, for example, a gas giant with roughly the same density as foam board. That means it could actually float in a bathtub (fun fact: so could Saturn). Like other exoplanets called “hot Jupiters,” this one is really close to its star — a “year,” one orbit, takes just five Earth days. One side always faces the star, just like one side of the Moon always faces Earth. That means it’s always hot and light on one half of this planet; on the other, night never ends. If you’re bummed out by cloudy days on Earth, consider that one side of Kepler-7b always has thick, unmoving clouds, and those clouds may even be made of evaporated rock and iron. And at more than 2,400 º F (1,316º C), Kepler-7b would be a real roaster to visit, especially on the dayside. It’s amazing to learn about how different exoplanets can be from Earth, but we’re glad we don’t live on Kepler-7b. —Kristen Walbolt, digital and social media producer/strategist, NASA's Jet Propulsion Laboratory.



1) ”The History of Earth Day,” URL: https://www.earthday.org/history/

2) https://www.earthday.org/earth-day-live/

3) ”NASA Observes Earth Day With Downloadable Art,” NASA/JPL Caltech, 17 April 2020, URL: https://www.jpl.nasa.gov/news/news.php?release=2020-074

4) Ellen Gray, NASA's Earth Science News Team, ”On Earth Day 50, NASA Researchers Look To the Future,” NASA Earth Feature, 21 April 2020, URL: https://www.nasa.gov
/feature/goddard/2020/on-earth-day-50-nasa-researchers-look-to-the-future

5) ”#EarthDayAtHome with NASA,” NASA, 16 April 2020, URL: https://www.nasa.gov/feature/goddard/2020/earthdayathome-with-nasa/

6) ”Down to Earth,” ESA Science & Exploration, 21 April 2020, URL: http://www.esa.int/ESA_Multimedia/Images/2020/04/Down_to_Earth

7) ”Earth Day: taking the pulse of our planet,” ESA Applications, 22 April 2020, URL: http://www.esa.int/Applications/Observing_the_Earth
/Space_for_our_climate/Earth_Day_taking_the_pulse_of_our_planet

8) ”Earth Day message,” ESA, 22 April 2020, URL: http://www.esa.int
/ESA_Multimedia/Videos/2020/04/It_can_be_done._-_an_Earth_Day_message

9) Svetlana Shekhtman, ”Nine Reasons We’re Grateful to Live on Earth,” NASA/GSFC Feature, 21 April 2020, URL: https://www.nasa.gov/feature/goddard/2020/9-reasons-we-re-grateful-to-live-on-earth


The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (herb.kramer@gmx.net).

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