From an Atmospheric River to a River of a Sediment

February 21st, 2017 by Adam Voiland

Credit: NASA Earth Observatory/VIIRS/Jesse Allen. More details about the image here.

In the past two months, weather reports in California, Oregon, and Washington have been filled with news of “atmospheric rivers” bringing copious amounts of rain and snow to the western United States. Atmospheric rivers are long, thin fingers of moisture that develop in the tropics and flow into higher latitudes. If one of them makes landfall, huge of amounts of rain and snow can fall in a short period.

Much of this moisture, of course, eventually finds its way back to the sea through rivers. When waterways are swollen and flowing rapidly, they also become rivers of suspended sediment, full of clay, mud, sand, and other debris. Though the flooding from atmospheric river events can be devastating, the enormous amount of sediment they send rushing into the sea can also be surprisingly beautiful.

For instance, on February 11, 2017, the Visible Infrared Imaging Radiometer Suite (VIIRS) on Suomi NPP acquired this remarkable view of rivers and streams spewing sediment into the Pacific Ocean. Close to the outlets of streams and rivers, sediment-rich waters appear brown. As the sediment dissipates and mixes into the ocean, the water appears teal.

Duane Waliser, a scientist at NASA’s Jet Propulsion Laboratory, recently tallied just how damaging atmospheric rivers can be for coastal areas. In a study published in Nature Geoscience, Waliser and a colleague showed that atmospheric rivers are among the most damaging storm types in the middle latitudes. Of the very wettest and windiest storms (those ranked in the top 2 percent), atmospheric rivers were associated with nearly half of them. Waliser and colleagues also found that atmospheric rivers were associated with a doubling of the typical wind speed compared to all storm conditions.

Image originally published by NOAA.

Satellite Images We Love

February 14th, 2017 by Adam Voiland

Image Credit: NASA Earth Observatory/Joshua Stevens

In celebration of Valentine’s Day, the NASA Earth Observatory staff took some time to look through our archives to find a few images that we absolutely love. You will find eight of our favorite scenes below: the islands of Mergui Archipelago, tea-colored water in James Bay, a snowy scene of Long Island, the intricate waterways of Musa Bay, an eddy of phytoplankton near South Africa, the Nardo racing ring in Italy, sea ice and icebergs in Antarctica, and a meandering river in the Amazon. Each staff member wrote a short note explaining why they chose the image.

Do you have a crush on NASA, earth science, and satellite imagery like we do? Get in on the fun by finding your favorite image from our archives and posting the link to the comment thread (and your social media sites of choice) with a few words explaining why you love the image. If you have trouble finding the perfect match by blindly searching our archives, you can also go to this page and sort by category, year, and month. You can also try our Visible Earth archive, where the images are conveniently categorized by what they show and which satellite sensor acquired them.

Image credit: NASA Earth Observatory/Landsat 5/TM. More details here.

This image is full of fantastic reminders about our planet and the science of Earth observation. Sediment flows, forests, and human settlement can all be seen in gorgeous color. But what’s more — the image was acquired by Landsat 5 back in 2004. We are currently two generations further in the Landsat constellation; this image is a vivid reminder of the quality and depth of that legacy. — Joshua Stevens, data visualizer

 

Image credit: NASA Earth Observatory/Landsat 8/OLI. More details here.

If you’ve ever read the blog FYFD or even spent time looking carefully at cream swirling around in your coffee, you’ll know why I love this image. There are times that fluids just going about their mundane business of mixing and flowing make patterns that are insanely beautiful. Check out our original story for a more detailed view of the von Kármán vortices swirling away from the small island in the middle of the Bay to see what I mean.  — Adam Voiland, science writer

 

Image credit: NASA Earth Observatory/Landsat 8/OLI. More info here.

Home is where the heart lies. In my case, that’s New York City and Long Island — my two homes. I grew up in both of these places, and love them both. This image shows dense snow that covered New York in February 2015. If Landsat 8’s Operational Land Imager (OLI) could zoom in farther, you might see my mom and me cross-country skiing on the beach, or my dog bounding through the hills of snow.  I still remember the enormous ice floes in Long Island Sound, which you can see in this image. — Pola Lem, science writer

 

Image Credit: NASA Earth Observtory/EO-1/ALI. More info here.

There’s a lot to this image I really like. The dendritic pattern of waterways and the sharp contrast that has against the strong straight linear features of man-made structures is quite striking. Also, the way that the warm, reddish-browns and the cool-toned blues and greens weave together is really compelling. Finally, I like the backstory of how we found this image: it was an accidental discovery made possible only because the satellite — Earth Observing-1 — produces a small number of images each day, making reading the entire list of images acquired (not just known objects of interest) possible for serendipitous discoveries like this. — Jesse Allen, data visualizer

 

Image credit: NASA Earth Observatory/Terra/MODIS. More info here.

After 6.5 years and 2500+ images since I joined EO, I have a hard time calling any image a favorite. But I thought of this one today because it pulls together many strands of my life. I have worked with scientists studying the Earth from space and with those studying the ocean from ships. I have long enjoyed learning and writing about the macrocosm and the microcosm — seeing things on both the grandest and the smallest of scales. And I have always preferred nonfiction, photography, and realism to abstract and impressionistic art. This phytoplankton bloom, which is tracing out the vortices of an eddy, looks like a blue rose in the sea. And while it looks like a painting, it is completely natural. It was created by the tiniest of organisms — phytoplankton — and by unseen, potent forces — deep ocean currents. It’s another day when reality is just as beautiful as any art. — Michael Carlowicz, managing editor

 

Image credit: NASA/International Space Station/Expedition 14. More info here.

Being an automotive enthusiast, as well as an amateur racer, I’ve always loved images of the Nardo Ring.  This racing circuit is a perfect circle, and massive in order to be used for vehicle testing.  Highways, city girds, and other roadways are often prominent features in astronaut photography, but the scale and precision of the Nardo Ring are impressive when set against the Italian farm fields.  It’s easy to see, even from up there, the impact the racing and automotive culture has on Italy, and the rest of the world.  — Paul Przyborski, programmer/dba/designer

 

Image credit: NASA Earth Observatory/EO-1/ALI. More info here.

I really like this image because of the variety of blue and white hues. There is young ice, old ice, icebergs that are trapped in sea ice, and all of it is accentuated by an oblique sun angle casting shadows and highlighting texture. — Kevin Ward, team leader

Image Credit: NASA Earth Observatory/Landsat 8/OLI. More info here.

If I’m not mountain biking, you will probably find me kayaking—a hobby partly inspired by regularly seeing incredible views of Earth’s rivers from space at work. What I love most about this image of Rio Mamoré in the Amazon Basin is how you can see how much the rivers meander and migrate over time. Interestingly, researchers studying rivers in this region found that the greater the amount of sediment from external sources (glacial, volcanic, or human activity), the more likely the rivers were to meander. — Kathryn Hansen, science writer

 

Using Satellites to Size Up the Severity of Crop Fires in Northern India

February 8th, 2017 by Adam Voiland with Hiren Jethva

NASA Earth Observatory images by Joshua Stevens, using VIIRS data from the Suomi National Polar-orbiting Partnership and the Fire Information for Resource Management System (FIRMS). The map shows fires detected on November 2, 2016.

When I was writing about the crop fires in northern India last fall, it was obvious that 2016 was a pretty severe burning season. For several weeks, large plumes of smoke from Punjab and Haryana blotted out towns and cities along the Indo-Gangetic plain in satellite images.

But I didn’t realize just how severe the fires were until Hiren Jethva, an atmospheric scientist at NASA Goddard Space Flight Center, crunched the numbers. By analyzing satellite records of fire activity, he found that the 2016 fires were the most severe the region has seen since 2002 in regards to the number of fire hot spots satellites detected. In regards to the amount of smoke detected, the 2016 burning was the most severe observed since 2004. He used data from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on Aqua and the Ozone Monitoring Instrument (OMI) on Aura to reach his conclusions.

Smoke and fire in northern India have become common in October and November during the last three decades because farmers increasingly use combines to harvest rice and wheat. Since these machines leave stems and other plant residue behind, farmers have started to use fire to clear the leftover debris away in preparation for the next planting.

For more details about how 2016 compared to past years, see the charts below, which Jethva prepared. His explanation for each chart is in italics.

Aqua Detected More Fires in 2016 Than During Any Year Since 2002

Chart by Hiren Jethva based on MODIS data.

The satellite-based sensor MODIS can detect the signal of fire hot spots, also called thermal anomalies, because the signal measured by the sensor in space in the thermal infrared bands appears to be an anomaly compared to the signal emanated from the background land. Since its launch in 2002, the MODIS on NASA’s Aqua satellite has detected thermal anomalies such as wildfires, agricultural fires, and gas flares on a daily basis.

The yearly evolution of total number of fires and Fire Radiative Power (FRP) — the heat energy produced from these fires — detected over Punjab and Haryana showed 2016 to be an anomalous year, with the highest number of crop residue fires (18,707) and the highest FRP in relation to the fires in all other years over the region. In comparison to 2015, the total number of fire hot spots detected over the region in 2016 was 43 percent higher; the difference is 25 percent if the hot spot counts are averaged over the last five years, i.e., 2011-2015. A careful look at the time-evolution of fire counts also reveals an increasing trend in the total number of fires over the region.

Punjab Skies Were Unusually Smoky 

Chart by Hiren Jethva based on OMI data.

These fires produced huge amounts of fine aerosol particles and trace gases, which can potentially impact the climate and degrade air quality drastically at ground level. NASA’s A-train sensors such as the Ozone Monitoring Instrument (OMI) on the Aura satellite and the MODIS on Aqua offer capabilities to measure the total amounts of airborne particles. The UV Aerosol Index (UV-AI), which is an excellent indicator of the column amounts of light-absorbing particles in clear as well as cloudy atmospheres, showed 2016 was the smokiest season on record since 2004.

 

Greener Fields and Larger Harvests Lead to More Fires

Many studies have shown that satellite measurements of the “greenness” of  crop fields prior to harvest and crop yield after the harvest are strongly correlated. The normalized difference vegetation index (NDVI), which is derived from satellite measurements of radiation at the red and near-infrared light, is one useful measure of greenness. As seen in the charts above, there seems to be a one-to-one relationship in NDVI measured by the MODIS sensor on Aqua prior to harvest (September) and the total number of fire hot spots observed during harvest season (Oct-Nov). This suggest that the increase in the number of fires is likely related to increasing crop yields.

February Puzzler

February 6th, 2017 by Pola Lem

Every month on Earth Matters, we offer a puzzling satellite image. The February 2017 puzzler is above. Your challenge is to use the comments section to tell us what part of the world we are looking at, when the image was acquired, what the image shows, and why the scene is interesting.

How to answer. Your answer can be a few words or several paragraphs. (Try to keep it shorter than 200 words). You might simply tell us what part of the world an image shows. Or you can dig deeper and explain what satellite and instrument produced the image, what spectral bands were used to create it, or what is compelling about some obscure speck in the far corner of an image. If you think something is interesting or noteworthy, tell us about it.

The prize. We can’t offer prize money or a trip to Mars, but we can promise you credit and glory. Well, maybe just credit. Roughly one week after a puzzler image appears on this blog, we will post an annotated and captioned version as our Image of the Day. After we post the answer, we will acknowledge the person who was first to correctly ID the image at the bottom of this blog post. We may also recognize certain readers who offer the most interesting tidbits of information about the geological, meteorological, or human processes that have played a role in molding the landscape. Please include your preferred name or alias with your comment. If you work for or attend an institution that you want us to recognize, please mention that as well.

Recent winners. If you’ve won the puzzler in the last few months or work in geospatial imaging, please sit on your hands for at least a day to give others a chance to play.

Releasing Comments. Savvy readers have solved some of our puzzlers after only a few minutes or hours. To give more people a chance to play, we may wait between 24-48 hours before posting the answers we receive in the comment thread.

Good luck!

A Shape-Shifting Volcanic Island

February 2nd, 2017 by Kathryn Hansen

Image courtesy of AVO/USGS.

Looking at Earth from space every day, we notice that nature takes on some curious shapes. (We have found, for example, features that resemble every letter of the alphabet.) The landform in the image above, which looks a lot like a human ear, is actually Bogoslof Island—a volcano in the Bering Sea that has been erupting in recent weeks. But the island didn’t always have an ear-like shape, and it might not look that way in the future.

Bogoslof has been erupting since mid-December 2016. We wrote about it a few weeks ago when satellite imagery showed a plume of steam and ash ejected from the volcano’s vent. Much of the volcano was (and remains) under water, with only a small part of the volcano’s top rising above the surface. Interaction of the vent with seawater was the reason that the plume contained so much steam. But by the end of January 2017, things had changed. The image above, from the Alaska Volcano Observatory (AVO), shows the island’s new shape after an eruption on January 30-31.

The image was described in more detail by Dave Schneider on the AVO website:

“Freshly erupted volcanic rock and ash have formed a barrier that separates the vent from the sea. This is the first time this has been observed since the eruptive sequence began in mid-December 2016. The vent is below sea level, and erosion of the ash deposits by wave or eruptive processes would allow sea water to flow into the vent again.”

Find more information and images describing Bogoslof and its changing form here.

In Coastal Peru, Fog Begets Life

January 31st, 2017 by Kathryn Hansen

 

It might seem unlikely that vegetation can survive in a sandy coastal environment that receives little rain, but plant communities along Peru’s southern coast have found a way.

In December 2016, we published the top image showing a unique perspective of fog. From space, you can see the vast expanse of marine stratocumulus sweeping inland to fill some of Peru’s deep valleys. It is the visible outcome of unseen atmospheric circulation and ocean currents.

From the ground, visibility would be limited (assuming the cloud layer is reaching all the way down to the ground). Depending on your location, experiencing fog might not be too unusual. In coastal Chile and Peru, it’s most common to get fog like this during the austral winter (June through August) and early spring. Plant communities called “lomas” depend on it for their survival.  Instead of relying on rainfall, the plants get much of their water by combing droplets out of the air as dense fog passes by.

Ralf Hesse, a scientist at the State Office for Cultural Heritage in Germany, has used remote sensing to study Peru’s lomas. He provided the second image above, which shows the view from a study site located about 80 kilometers (50 miles) northwest from the top-left corner of the satellite image. The loma pictured is composed of the species Tillandsia. But depending on the location, lomas can contain anything from grasses and shrubs to small trees.

 

Have Your Satellite Imagery and Eat It, Too!

January 27th, 2017 by Pola Lem

Three thick layers of cake and frosting sat atop Jeff Schmaltz’s kitchen counter. The programmer had completed a 3-D model of a GIBS tile pyramid; it was his entry into a collegial science bake-off at NASA’s Goddard Space Flight Center. But there was more to this cake than flour and eggs and sugar.

This tile pyramid cake shows a view of the world with Antarctica represented as the largest continent on the map. Credit: Susan Schmaltz.

If you have ever browsed Earth science imagery and data using the online tool Worldview, then you have also used GIBS, Global Imagery Browse Services. GIBS is like a gear behind a clock face, a mechanism that keeps the hands moving. Schmaltz and his colleagues rely on it daily as they assemble images of our dynamic planet. (Worldview is a free and publicly available Earth science browser used by scientists and non-scientists, including the NASA Earth Observatory team.)

How It Works

GIBS ingests and organizes satellite data to create a global mosaic. Then, it chops down the data into digestible bits—like that image tile pyramid that Schmaltz recreated with cake—so that users can quickly view Earth as seen from space.

Zoomed out in a broad view, you see just the top tile, the whole Earth in low resolution (like the top layer of the cake). Zoomed in, you see one tile covering a smaller region of the earth but in more detail (like a square from the bottom layer of the cake). On an interface like Worldview, which allows users to scroll and view daily images from the entire surface of Earth, an architecture like GIBS is necessary to keep the site running quickly.

“It’s very fast, and there’s not a lot of computing going on,” Schmaltz said. GIBS does the same thing that Google Maps does: it summons only the data the user requests. By dealing in tiles, the program can serve many people at once without getting bogged down.

GIBS uses tiles (512 x 512 pixels) to speed up data processing. Credit: The Open Geospatial Consortium (OGC).

Way Back When

Not long after NASA launched the Terra satellite in late 1999, the U.S. experienced a record fire season: A record 8.4 million acres burned in the year 2000. At the time, it could take weeks for data from Terra’s MODIS instrument to be processed into images. Scientists hoped that a quicker turnaround might translate into a more informed response to fires. As result, NASA created a near-real time fire pixel product.

Seventeen years later, scientists can visit Worldview to see roughly 150 near-real time data sets from different satellites and sensors as the clouds and snow cover change each day. Air pollution, vegetation cover, dust, smoke are just a few of the data layers users can view.

Credit: NASA.

P.S. To make Jeff’s satellite cake, follow his grandmother’s recipe below:

Ingredients:

  • 1 cup + 2 tablespoons of flour
  • ¾ cup + 2 tablespoons of sugar
  • 1 ½ teaspoon of baking powder
  • ½ teaspoon of salt
  • ¼ cup of oil (salad or olive is fine)
  • ¼ cup + 2 tablespoons of cold water
  • 2 egg yolks (keep whites for later)
  • 1 teaspoon of vanilla
  • 1 ½ oz. (3 squares) of baker’s unsweetened chocolate, grated

Directions:

Mix dry ingredients together. Measure oil, water, egg yolks, and vanilla into a measuring cup and mix; then add to dry ingredients and beat until smooth.

Beat 2 egg whites + ¼ tsp. cream of tartar until stiff. Fold into batter. Slowly mix in grated chocolate.

Bake in ungreased 8×8 pan at 350 degrees for 20-25 minutes. Check with toothpick when done. Cool on a rack. Goes best with chocolate frosting. (Schmaltz uses the recipe on the side of a Hershey’s can.) Alternately, you can top the cake with an edible print of a satellite image.

Credit: Adam Voiland.

Image Credit: NASA Earth Observatory/Aqua/MODIS/Jeff Schmaltz

In August and September 2015, a massive dust storm swirled across the Middle East. After reporting on the storm, I read a fair amount of speculation — but no clear answers — as to what kicked up such an unusually large amount of dust. Several reports made the case that the ongoing war in Syria was a contributing factor. The war, some scientists speculated, had increased the military traffic over unpaved roads and had led farmers to abandon their land.

Now a new study led by a researcher from Duke University argues that the war was not an important cause. By analyzing satellite data of vegetation cover before the war, the researchers concluded that the conflict did not have much effect on vegetation. (Vegetation helps hold sand and soil in place.) In fact, the satellites observed that agricultural activity was healthy in 2015 in comparison to earlier years.

Rather, the research team found that the key drivers of the dust storm were meteorological. The summer of 2015 was unusually hot and dry compared to the past 20 years, meaning more dust was available and in a condition that winds could easily lift. So when an unusual cyclonic wind pattern developed in late August and persisted for more than a week, a mega dust storm was born.

Read a press release about the study from Princeton University, and read the full study in Environmental Research Letters. To reach their conclusion, the researchers used Aerosol Optical Depth and Normalized Difference Vegetation Index (NDVI) observations from NASA’s Moderate Resolution Imaging Spectroadiomters (MODIS), and meteorological simulations from the Weather Research and Forecasting (WRF) model. You can view several types of satellite imagery of the storm, which began on August 31 and peaked on September 8, on NASA’s Worldview browser.

 

Something Swirling in the Sea

January 20th, 2017 by Kathryn Hansen

Almost every volcano is interesting from a scientific perspective, but there are just too many eruptions for us to cover every single one. Instead we tend to focus on eruptions that have the potential to affect people. Or, occasionally our satellites return images that simply look so unique that we find the time to cover them. The plume recently ejected from Alaska’s Bogoslof Volcano was noteworthy for both reasons.

Bogoslof, which has been erupting since mid-December 2016, gave rise to a compelling two-tone plume. Are materials being ejected from a vent that is still under water? (Most of the volcano is below the surface of the sea.) The volcano’s interaction with seawater explains the white steam. But if the vent is not yet above water, then how did such a large, dark plume of ash reach so high in the atmosphere? Scientists at the Alaska Volcano Observatory continue to monitor the remote volcano and perhaps answers will be forthcoming as the eruption evolves.

Also intriguing are the swirls of blue visible in the image above. The Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured the image on January 7, 2017. My first thought was that the color was caused by a bloom of phytoplankton. The milky blue color looked about right. And iron from eruptions have previously been shown  to provide the nutrients needed for blooms to flourish. But when I asked the experts, the general consensus was that while you can’t rule out a bloom, there was another more likely explanation for the swirls.

According to ocean scientist Norman Kuring of NASA’s Goddard Space Flight Center:

“Phytoplankton don’t normally bloom in the Bering Sea during winter because there’s not a lot of sunlight and because winter storms deepen the mixed layer which also keeps the plankton more in the dark. Wave action can resuspend bottom sediments, and that may be happening farther east along the Aleutian chain in the January 7 image where the water is relatively shallow. Bogoslof Island is beyond the shelf break, however, so bottom resuspension is less likely. Ash in the water seems most probable…. I wouldn’t expect the Bering Sea to be nutrient limited in the winter, so I don’t expect an ash-based phytoplankton boost.”

In short, the swirls are probably ash in the water. The phenomenon is not unprecedented. We have previously published images of the occurrence here and here. But as Kuring reminds us, “the only way to know for sure would be to sample the water directly.”

 

Waiter, There’s Salt in My Lake

January 18th, 2017 by Pola Lem

In some parts of the world, saline lakes are common features. Take, for instance, the image below, from our January 2017 article about fires in Argentina. But saline lakes are an environment unto themselves.

Lakes cover about 4 percent of the Earth’s land surface. Many of the largest ones (by area) are salty: Utah’s Great Salt Lake, the Caspian Sea (arguably the world’s biggest lake), Iran’s Lake Urmia, and the Dead Sea. Unlike marine and brackish waters, saline lakes typically form inland, and do not connect to the ocean. They tend to be ephemeral, filling with water in periods of increased rainfall, and drying out under the Sun.

In general, the saltier the lake, the fewer animals that can tolerate it. Yet a number of invertebrates call saline lakes home. Brine shrimp, for instance, have evolved to live in the salty, low-oxygen environment of the Great Salt Lake. The shrimp—also called “sea monkeys”—can survive even as water recedes. They are so plentiful, in fact, that fishermen corrale them using oil booms in an annual harvest.

Image: NASA Earth Observatory/Jeff Schmaltz

 

Just how salty are these lakes? That depends on location and season. The Dead Sea has a salinity of 34 percent, while the Great Salt Lake varies between 10 and 30 percent; the same is true of Lake Urmia. (For comparison, open ocean waters average a 3.5 percent salt content.)

Australia’s scorching hot weather and scant rainfall make it a hotbed for saline lakes—thousands of them. In her story on the colorful salt lakes Down Under, my colleague Kathryn Hansen describes how they formed:

Millions of years ago, declines in rainfall caused river flows to ebb and river valleys to fill in with sediment. Wind then sculpted the loose sediment to form the lake basins that remain today. (The wind also sculpted some of the lighter sediments into parallel dunes that fringe each lake downwind to the east-southeast.) Some of the lakes now fill with runoff directly from the Stirling Range; others are controlled primarily by groundwater.

The lakes below in Western Australia range from pea soup-brown to pinkish in hue. Their color changes based on sediments, aquatic and terrestrial plant growth, water chemistry, algae, and hydrology.

Image: NASA Earth Observatory/Joshua Stevens

At Urmia, the rise and fall of lake also has an effect on water color:

The color changes have become common in the spring and early summer due to seasonal precipitation and climate patterns. Spring is the wettest season in northwestern Iran, with rainfall usually peaking in April. Snow on nearby mountains within the watershed also melts in the spring. The combination of rain and snowmelt sends a surge of fresh water into Lake Urmia in April and May. By July, the influx of fresh water has tapered off and lake levels begin to drop.

The fresh water in the spring drives salinity levels down, but the lake generally becomes saltier as summer heat and dryness take hold. That’s when the microorganisms show their colors, too.

While many salt lakes vary in size according to rainfall, some like Lake Urmia, have been shrinking in recent years.

Image: NASA Earth Observatory/Joshua Stevens

Hot, sunny days help create saline lakes by evaporating massive amounts of water, but salt lakes can also occur in cold climes. For instance, Don Juan Pond sits in Antarctica’s McMurdo Valley, where winter temperatures can drop to -50 degrees Celsius (-58 degrees Fahrenheit). Don Juan is so salty that waters rarely freeze. Its extreme environment resembles that of Mars. While the lake is far too salty and cold for even salt-loving brine shrimp, it does house microorganisms, Brown University geologist, Jay Dickson, told the NASA Earth Observatory.

“There is certainly biology in the vicinity of the pond and some evidence for biologic activity in the pond itself, but this activity could be explained by abiotic processes,” Dickson said. “Mars has a lot of salt and used to have a lot of water.”

Image: NASA Earth Observatory/Jesse Allen