Marine plankton brighten clouds over Southern Ocean

Satellites use chlorophyll’s green color to detect biological activity in the oceans.

The lighter-green swirls are a massive December 2010 plankton bloom following ocean currents off Patagonia, at the southern tip of South America.

Image via NASA

From NASA

New research using NASA satellite data and ocean biology models suggests tiny organisms in vast stretches of the Southern Ocean play a significant role in generating brighter clouds overhead. Brighter clouds reflect more sunlight back into space affecting the amount of solar energy that reaches Earth’s surface, which in turn has implications for global climate.
The results were published July 17 in the journal Science Advances.
The study shows that plankton, the tiny drifting organisms in the sea, produce airborne gases and organic matter to seed cloud droplets, which lead to brighter clouds that reflect more sunlight.

"The clouds over the Southern Ocean reflect significantly more sunlight in the summertime than they would without these huge plankton blooms," said co-lead author Daniel McCoy, a University of Washington doctoral student in atmospheric sciences.
"In the summer, we get about double the concentration of cloud droplets as we would if it were a biologically dead ocean."

 Tiny ocean life contribute to clouds directly, by being lofted up with sea spray, and indirectly, by producing sulfurous gas.Daniel McCoy / University of Washington
Daniel McCoy / University of Washington

Although remote, the oceans in the study area between 35 and 55 degrees south is an important region for Earth's climate.
Results of the study show that averaged over a year, the increased brightness reflects about 4 watts of solar energy per square meter.

McCoy and co-author Daniel Grosvenor, now at the University of Leeds, began this research in 2014 looking at NASA satellite data for clouds over the parts of the Southern Ocean that are not covered in sea ice and have year-round satellite data.
The space agency launched the first Moderate Resolution Imaging Spectroradiometer (MODIS), instrument onboard the Terra satellite in 1999 to measure the cloud droplet size for all Earth's skies.
A second MODIS instrument was launched onboard the Aqua satellite in 2002.

 Marine stratocumulus clouds stretched across the southern Indian Ocean in this image taken by NASA's Aqua satellite in early March 2013.

Clouds reflect sunlight based on both the amount of liquid suspended in the cloud and the size of the drops, which range from tiny mist spanning less than a hundredth of an inch (0.1 millimeters) to large drops about half an inch (10 millimeters) across.
Each droplet begins by growing on an aerosol particle, and the same amount of liquid spread across more droplets will reflect more sunlight.

Using the NASA satellite data, the team showed in 2014 that Southern Ocean clouds are composed of smaller droplets in the summertime.
But that doesn't make sense, since the stormy seas calm down in summer and generate less sea spray to create airborne salts.

 Wave clouds form over Île aux Cochons in the Southern Ocean.

The new study looked more closely at what else might be making the clouds more reflective.
Co-lead author Susannah Burrows, a scientist at the Pacific Northwest National Lab in Richland, Washington, used an ocean biology model to see whether biological matter could be responsible.
Marine life can affect clouds in two ways.
The first is by emitting a gas, such as dimethyl sulfide released by Sulfitobacter bacteria and phytoplankton such as coccolithophores, which creates the distinctive sulfurous smell of the sea and also produces particles to seed marine cloud droplets.
The second way is directly through organic matter that collects at the water's surface, forming a bubbly scum that can get whipped up and lofted into the air as tiny particles of dead plant and animal material.

 The exact boundaries of the Southern Ocean are as up in the air as its many clouds.

Credit: NASA

By matching the cloud droplet concentration with ocean biology models, the team found correlations with the sulfate aerosols, which in that region come mainly from phytoplankton, and with the amount of organic matter in the sea spray.
"The dimethyl sulfide produced by the phytoplankton gets transported up into higher levels of the atmosphere and then gets chemically transformed and produces aerosols further downwind, and that tends to happen more in the northern part of the domain we studied," Burrows said.
"In the southern part of the domain there is more effect from the organics, because that's where the big phytoplankton blooms happen."
Taken together, these two mechanisms roughly double the droplet concentration in summer months.
The Southern Ocean is a unique environment for studying clouds.
Unlike in other places, the effects of marine life there are not swamped out by aerosols from forests or pollution.
The authors say it is likely that similar processes could occur in the Northern Hemisphere, but they would be harder to measure and may have a smaller effect since aerosol particles from other sources are so plentiful.

Links :

• Scientific American : Tiny Ocean Plants Geoengineer Brighter Clouds

Avoiding rock bottom: How Landsat aids nautical charting

A recent NOAA nautical chart of the Beaufort Sea

(Chart 16081: Alaska-Arctic Coast, Scott Pt. to Tangent Pt. ).

The massive thumb-shaped shoal at the top left was identified by NOAA using Landsat satellite data.

From NASA  by Laura Rocchio

On the most recent nautical chart of the Beaufort Sea where the long narrow Tapkaluk Islands of Alaska’s North Slope separate the sea from the shallow Elson Lagoon (Nautical Chart 16081) a massive shoal is immediately noticeable just west of the entrance to the lagoon.
On the chart it looks like a massive blue thumb jutting out into the sea.
The National Oceanographic and Atmospheric Administration (NOAA) identified this prodigious, 6-nautical mile-long, 2-nm-wide shoal using Landsat satellite data.

It was sometime around 1950 that a hydrographic survey ship last plied these waters taking water depth measurements along its path using a single-beam echo sounder and visual navigation.
These data points were laboriously merged with shoreline and hazard information to create this chart, Alaska-Arctic Coast, Scott Pt. to Tangent Pt.
Given the low ship traffic in the region, updating this chart was lower priority than other high-traffic areas.
But things change—fishing and water-commuting traffic have risen in the area, as has marine tourism; but that’s not all: bottom depths have changed too as currents, erosion, and sediments have worked together to sculpt the seafloor.

In NOAA’s Office of Coast Survey, the Marine Chart Division is responsible for updating the suite of over 1000 nautical charts that keep mariners in U.S. waters safe.
Their mandate covers all U.S. territorial waters in the U.S. Exclusive Economic Zone (EEZ), a combined area of 3.4 square nautical miles that extends 200 nautical miles offshore from the nation’s coastline.
The U.S. has the largest EEZ of all nations in the world, but it ranks behind 18 other nations in the number of vessels with hydrographic surveying capabilities.
Their job is sizable and expensive.
While the Army Corps of Engineers is responsible for maintaining shipping channel depths, providing bathymetry everywhere else in U.S. waters is NOAA’s duty.

Keeping waterways safe is a massive undertaking

The responsibilities of NOAA’s Marine Chart Division are immense.
Charged with providing accurate charts for mariners, NOAA cartographers need to know when existing charts are out-of-date.
To determine if charts are current, they employ lots of tools.
They monitor navigation hazard reports submitted by mariners; they watch ship traffic patterns using vessel positioning information (via the Automatic Identification System); and more-and-more they are turning to satellite information, especially Landsat data.

The field of Satellite Derived Bathymetry (SDB), has been around for nearly a half-century now, but the advent of free Landsat data in 2008 together with the 2013 launch of the more-advanced Landsat 8 satellite and a shift in thinking about SDB products, have led to a reinvigorated use of satellite data in NOAA’s Marine Chart Division.

The concept of SDB is that different wavelengths of light penetrate water to differing degrees.
The smaller the wavelengths (e.g. blue and green light) penetrate water more than longer-wavelengths (e.g. near infrared, shortwave infrared).
When water is clear and the seafloor bottom is bright (sandy for example) estimates of depth can be made by modeling the depth of light penetration based on the amount of reflectance measured by the satellite.
And when multiple visible-wavelength spectral bands are used together, the effects of seafloor reflectance variability and water turbidity are lessened.
These modeled depth measurements typically do not meet hydrographic accuracy standards, so in the past SDB measurements were eschewed.

“There’s been a shift in the way we think,” Lieutenant Anthony Klemm, a NOAA Corps Officer in the Office of Coast Survey’s Marine Chart Division, explains,
“In the past, if a measurement wasn’t made by the Army Corps or a NOAA survey ship, we didn’t want to use it, but now we are opening up to other technologies to evaluate the health of our current chart suite.”

Because of this sea change in thinking and faced with the daunting job of deciding which charts were most in need of updating, NOAA hydrographers revisited the use of SDB using freely available Landsat data as a viable tool to help them do their jobs.

“NOAA has now been using Landsat imagery for chart adequacy assessment and mission planning,” Shachak Pe’eri, a Research Professor at the Joint Hydrographic Center at the University of New Hampshire, says.

The Joint Hydrographic Center, a think-tank of researchers investigating technology and mapping challenges in NOAA’s Office of Coast Survey, realized that Landsat SDB could be an important reconnaissance tool.
A single Landsat image is about 100 nautical miles across and affords a wide overview of a coastal area.
Maps of SDB can be compared with existing nautical charts.
Places where depth patterns do not match are more closely examined.
Has the seafloor changed in this area?
If an area looks shallower than what is presented in the chart and if there is a reasonable amount of vessel traffic or corroborating mariners’ reports in the area, the chart location is tagged as a higher-priority candidate for hydrographic mapping—i.e. sending out a hydrographic ship to make depth measurements using sonar (multi-beam or single-beam).

Multi-beam sonar provides very accurate and comprehensive bathymetry, but for the amount of water NOAA is responsible for charting, these expensive ships are in short supply.

Klemm has been out on hydrographic voyages, and knows well the amount of time and effort that goes into gathering bathymetry information.
He is excited about the prospect of formally incorporating Landsat SDB into his workflow.

“SDB products to evaluate the current state of existing bathymetry representation is pretty amazing because of the temporal resolution of the satellite data—a little over every two weeks and you get a new shot of an area,” Klemm describes.
Landsat 8’s orbit puts it back over a given location every sixteen days.

Because satellites like Landsat can provide “quantifiable information related to the amount of change since the last hydrographic survey,” as Pe’eri wrote, SDB information can figure prominently into the determination of where new hydrographic surveys are most needed.

Pe’eri and Klemm have been working on a NOAA policy about the use of SDB. They are outlining how to use SDB to prioritize hydrographic surveys using a chart adequacy assessment procedure they have developed.
They are also working on a policy of how to update a chart with features found using satellite imagery.
“These charts are considered intermediary, but they can be made publicly available and used until a proper hydrographic survey can be performed,” Pe’eri explains.

Landsat is good at identifying new shoals, like that big 12 nm thumb-shaped shoal off of Alaska’s North Slope.
And NOAA thinking is that it is better to amend charts to tell mariners that satellites indicated a shoal, even though exact depths cannot be provided until the next hydrographic survey.

Deriving bathymetry with Landsat for 43 years

Uncharted shoals have sunk many ships. In the late 1960s, research groups began to experiment with remote bathymetry using multispectral airborne data in an effort to make measurements over large tracts of coastal waters in search of navigational hazards and shifting bathymetry.
With the launch of Landsat 1 in 1972, these newly developed methods could be used with data collected by the satellite’s Multispectral Scanner System and its wide 100 nm-wide images—satellite derived bathymetry was born.

In 1975, NASA teamed with famed oceanographer Jacques Cousteau to conduct an ocean bathymetry experiment using Landsat data to measure water depth in the Bahamas and off of Florida’s eastern coast.
Cousteau’s ship, the Calypso, anchored over a study site as Landsats 1 and 2 collected data from overhead, while they simultaneously took depth measurements using the ship’s sonic depth finder.
In this pre-GPS timeframe, LORAN-C radio measurements were used for locating the boat position.
They also dove to the seafloor to take in situ reflectance measurements with a submarine photometer.
This early experiment proved the feasibility of mapping shoals in clear water to depths equal to or greater than those needed for safe shipping.

The International Hydrographic Office, an inter-government organization concerned with making the seas navigable, had once classified shoals as navigational hazards between 0 and 17 meters (56 feet) below the surface, but with the advent of supertankers with drafts of over 20 meters (65 feet) and the capacity to carry massive amounts of oil, shoal definitions had to be broadened.

A year later, a Landsat 2 image acquired on March 29, 1976 revealed a major uncharted 8-km long reef in the Indian Ocean’s Chagos Archipelago: “There was a major reef or bank where the chart showed safe, deep water and some banks appeared to be out of position by more than 15 km relative to the nearest land,” wrote James Hammack, a participant in the NASA/Cousteau experiment and a cartographer with the Defense Mapping Agency’s Hydrographic Center (now part of the National Geospatial-Intelligence Agency).

 Colvocoresses Reef in the GeoGarage platform (NGA chart #61610)

Within a few months, the newly found reef, named Colvocoresses Reef after the USGS cartographer who identified the feature on the Landsat image, was added to DMA nautical chart 61610.
In the interim, Notice to Mariners were sent out to warn sailors in the region.

Based on the success of the NASA/Cousteau and Chagos Archipelago experiments, DMA requested that Landsat data be collected globally over coastal areas.
This data was used to “augment the completeness” of it nautical chart products.
DMA also used Landsat data to visually verify ship-reported navigational hazards.

 Star Reefs Passage in the GeoGarage platform (AHS 519 chart)

Some other documented cases of Landsat data providing critical information to navigation include a safe deep passage through Papua New Guinea’s Star Reefs, which was first discovered using Landsat imagery.
The Australian Royal Navy ship Flinders confirmed this passageway, which enabled ships to more quickly travel from Australian ports to East Asian ones.

 Red Sea near Al Qunfidha (UKHO chart) with the GeoGarage platform

Likewise, British Admiralty Chart 322 of the Red Sea near Al Qunfidha had to be completely revised after it was compared with Landsat data.

In 2006, 75 shallow-water features such as reefs, shoals, and seamounts where discovered or found mislocated with the use of Landsat 7.

Landsat aids hydrographic offices around the world

The International Hydrographic Organization and the United Nations’ Intergovernmental Oceanographic Commission jointly create an authoritative, publicly available, global bathymetry map known as the General Bathymetric Chart of the Oceans, or GEBCO. GEBCO charts have been published since 1903.
Despite this heritage, only about a tenth of the ocean floor has been mapped.

Satellite Derived Bathymetry measurements overlaid on a chart of Plymouth Bay in Massachusetts. The red indicates shallow waters.

Here, the SDB indicates that the the shoaling of Brown’s Bank has shifted since the chart’s creation.

GEBCO is no stranger to SDB.
They have been aware of its capabilities for decades.
But now that Landsat data are publically and freely available it is getting more and more use—as no doubt the European Space Agency’s Sentinel-2A, with spectral bands similar to Landsat 8, will as well.

The GEBCO companion how-to guide for creating bathymetric charts, called The GEBCO Cookbook, includes a chapter on using Landsat to derive bathymetry.
For cash-strapped national hydrographic offices, using free Landsat data to assess the adequacy of existing charts is essential, allowing them to allocate scarce resources with maximum impact to mariner safety.
SDB alone does not meet IHO accuracy standards, but its use as a complimentary prioritization and planning tool is key.

SDB measurements can also “be used to infill regions in remote or inaccessible areas where no (or poor) bathymetry data exists,” shares Stephen Sagar, an Aquatic Remote Sensing Scientist with Australia’s National Earth and Marine Observation Group.

NOAA, as a major Landsat user, has been sponsoring international GEBCO students from around the world (Kenya, Sri Lanka, Ecuador, Philippines, etc.) and teaching them how to use SDB to update charts in their home offices.
This summer from July 14–16, NOAA hosted a workshop to share this knowledge in the confidences that using SDB will make mariners worldwide more safe.
Hydrographers from 11 countries attended. The workshop was a big success and more workshops are planned for 2016.

NOAA: thinking big about SDB

Water clarity has been a limiting factor when it comes to SDB.
If waters are too turbid (full of sediments that obscure light reflectance from the seafloor), then bathymetric measurements cannot be made.

The inability of longer wavelengths, such as shortwave infrared light, to deeply penetrate water allows hydrographers to map shoreline change.
But when concentrations of suspended sediments are great enough to thwart penetration by shorter wavelengths, SDB by definition suffers.
But in NOAA’s Marine Chart Division, researchers are thinking outside of the SDB-box.

Pe’eri, in a collaborative study with NOAA and the U.S. Coast Guard, has pioneered turbidity mapping as a proxy for bathymetric measurements.
In enclosed waterbodies with strong currents, such as bays and sounds, turbid channels show up on Landsat imagery—and these turbid channels illuminate where currents are carving deeper channels that are safe for boat passage.

Landsat 8 image of In Bechevin Bay, the easternmost passageway between the Gulf of Alaska and the Bering Sea.

This natural color, pan-sharpened image was acquired on May 14, 2014.

Image processing by Jesse Allen, NASA Earth Observatory

 Bechevin Bay with the GeoGarage platform

Back in the arctic, where near-shore changes occur rapidly because of seasonal sedimentation and erosion, new SDB techniques like turbidity mapping are preventing maritime mishaps.
In Bechevin Bay, where the easternmost passageway between the Gulf of Alaska and the Bering Sea provides fisherman with a shortcut for three ice-free months a year, the location of sand bars can shift significantly because of melting ice in this narrow passage.
With the help of Landsat SDB turbidity maps, the new locations of these sandbars can be estimated. Recently this has led to the discovery of a new, straighter, and more geologically stable channel.

“SDB estimated from Landsat turbidity maps can help guide NOAA charting craft when they are mapping the channel each year and placing channel marking buoys.
This saves time and it makes the process safer,” Pe’eri says.
“With insufficient knowledge of sandbar locations, the NOAA craft risk running aground and crew can be thrown overboard when that happens.”

Pe’eri’s team has also developed a multi-image method to help separate clear and turbid waters using Landsat data.
Techniques such as turbidity mapping will grow increasingly important for navigation planning as warming waters enable more industrial development of the Arctic and set the stage for international shipping routes.

NOAA’s Marine Chart Division has made Landsat a prominent tool in their charting toolbox—especially Landsat 8 with its new deep blue band, improved signal-to-noise and greater dynamic range (12-bit).

“Landsat 8 is overwhelmingly better,” Pe’eri says citing the new satellite’s additional cirrus band which helps him better account for atmospheric noise that can counter accurate SDB and Landsat 8’s better radiometric resolution (which means more signal, less noise, and more measurement fidelity).
But it’s not just SDB that this innovative office is utilizing.
They are also watching traffic patterns using the Automatic Identification System (AIS) and even light communication from recreational boaters, fishermen, tugboats, and larger vessels, and together with bathymetry measurements are prioritizing which charts are in perilous need of revision.

“We’re making charts safer up there,” Klemm says talking about the recent Beaufort Sea chart revisions, “and that’s so exciting.”

Links :

• Hypack : Reconnaissance surveying of Bechevin Bay, AK using SDB (paper)

The ultra-rich dive into a new obsession

The Triton 3300/3 is one of the most popular submersible and it can take a pilot and two passengers.

From BBC by Eric Barton

Tucked away in an industrial park in Vero Beach, Florida, 34-year-old engineer John Ramsay is painstakingly drafting a design for a submarine that will be able to reach the five deepest points in the ocean.
The catch?
It's a personal vessel for a billionaire.
“It’s going to be a world- or certainly industry-changing vehicle,” Ramsay said.
The $25m, two-man submarine will take six months to design and another two years to build by Triton Submarines.
“Nobody has built a deep-going [personal] vehicle that has been used again and again, but that’s what we are trying to do.”
His client is one of several who see the ocean depths as a new playground.
A new breed of billionaires is tapping into their inner Jacques Cousteau — the famous undersea explorer — and they're willing to pay big.
With pricetags starting at a $3m, and requiring a yacht to park on, these personal submarines are not only for adventure, but also for their owners to help advance research and exploration in ways that weren’t dreamed about a decade ago.
“Part of this trend is that it is cool to have a submarine and part of it is that a private person can support research with it,” said Charles Kohnen, owner of submarine builder SEAmagine Hydrospace Corp in California.
“This is not just an effort to go where no man has gone before. This is going where no man has gone before — and come back to tell about it.”



The way forward

Still nascent, the personal submarine industry comprises four companies that account for just 20 to 30 privately owned and manned subs across the globe, according to Kohnen, an early pioneer who sold his first sub in 2000.
These sub owners frequently offer charters, at a price often up to $30,000 a day.
Some of these vessels have been rented out by other billionaires looking for a new holiday adventure, while others have been lent to research groups to discover new sea life or explore shipwrecks.
Few research organizations can, after all, afford to buy a submarine, let alone pay for upkeep and maintenance or cover the cost of the expensive ship that's required to transport it out to sea.
So, teaming up with a private owner has proven to be one promising strategy.

In 2013, researchers traveling in a privately owned submarine off the coast of Japan filmed a giant squid in its natural habitat for the first time.
And, in March of this year, a team using submarines owned by Microsoft co-founder Paul Allen found the Japanese battleship Musashi, which had been sunk off the coast of the Philippines in World War II.
Sometimes, however, the thrill of discovery lies purely with the submarine owner.
In 2012, filmmaker James Cameron broke a record for the deepest solo dive when he used a sub he owned to explore the Mariana Trench, the deepest spot in the oceans, located in the western Pacific. Cameron’s vehicle wasn’t designed for multiple trips into the extreme pressure of deep water and was retired after its only trip.

Beautiful underwater footage filmed in February 2015 using a small personal submarine from SEAmagine

The diving took place at Cocos Island in Costa Rica in conjunction with Misión Tiburón an organization that promotes the conservation of sharks and other marine species.

The video shows the abundance of sea life at Cocos’ marine sanctuary from the shallow depths to the very deep unexplored regions where a rare Prickly Shark was found during this expedition at a depth of 340m (1115 ft).

Most private subs reach depths of 1,000m or less.
The biggest construction challenge remains the compartment that holds passengers, which become compromised when under pressure at depth.
Triton’s subs include a 6.5-inch-thick acrylic passenger bubble made in Germany at a cost of about $1m.
To go deeper, the sub must be far more durable, including a sphere of ultra-thick glass that could cost four or five times as much, Ramsay said.
Just how effective these private owners can be at research or exploration is unclear, said George Bass, professor emeritus at the Texas A&M University Nautical Archaeology Program.
Bass is one of the world’s most prolific hunters of shipwrecks, especially in the Mediterranean.
Using a SEAmagine submarine off the coast of Turkey, he once found 14 wrecks in a month.
But Bass doubts that private owners could have the same kind of luck.
“It’s possible [that private sub owners] could stumble on a shipwreck or a new discovery,” Bass said.
“But it takes a lot of research and knowledge to make that happen.”

 Crystal Cruises has announced plans for an "extravagantly appointed yacht" featuring submarines offering underwater weddings (source : The Telegraph)

In the name of science

In Costa Rica, a submarine named DeepSee is being used by adventure travellers, researchers, and scientists for dives predominantly around Cocos Island, about 350 miles off the mainland.
With its unique cross currents, the water surrounding the islands is rich with rare coral and marine life, from crustaceans to whale sharks.
DeepSee’s owner, an eponymous private company, allows researchers from the University of Costa Rica to take the sub down for free, said operations manager Shmulik Blum, and they sometimes find new sea life never seen before.

 This video is about a dive with the DeepSea Submarine to 300+ m depth at Cocos Island, Costa Rica

Two years ago, the Costa Rican researchers discovered an entire new family of coral, the kind of discovery that hadn’t been made in 40 years, Blum said.
The new, soft coral is in waters so deep that it never sees light and lacks any pigment.
Using DeepSee’s robotic arm, researchers scooped up a sample that they later analysed in the lab.
“Usually, the lack of access to waters this deep limits the ability to learn about it,” Blum said.
“Once we can get down there, it gives us access to an entirely new world.”



Blum was speaking by phone from DeepSee’s office in the small port of Puntarenas.
Hours later, he and his submersible team would be making the day and a half journey to the Cocos Island for a new set of dives.
“Maybe we’ll find something new this time too,” he said.
“You never know."

Links :

• YouTube : Ultra-Luxury Private Submarine Comes With a Pool 
• GizMag : DeepFlight Dragon set to usher in the era of the personal submarine

The essence of surfing

Dreams, freedom, passion. But also fear and boundaries to break.

This is the essence of surfing.

Image of the week : comparing two 'Blue Marble' photos of Earth

From NYTimes

On Tuesday we shared NASA's new photo of a fully illuminated Earth.
(see : NASA website : 1972 / 2015 )
This is an update to the “Blue Marble” photo taken by Apollo 17 astronauts in 1972, more than four decades ago.

Here, you can compare the two.

“How perfect North America looks. I am still amazed by how the oceans dwarf the continents,” Jim Corradino of Norwalk, Conn., wrote us.

“There’s something remarkable about a single snapshot of the Earth — an intact view of our planet in its entirety, hanging in space,” the astronaut Scott Kelly observed in an essay on Medium.
He explained what makes these images so special.
Along with the challenge of getting far enough away to get the entire Earth into a single frame, there is the matter of lighting.

“In order to view the Earth as a fully illuminated globe, a person (or camera) must be situated in front of it, with the sun directly at his or her back,” he wrote.
“Not surprisingly, it can be difficult to arrange this specific lighting scheme for a camera-set up that’s orbiting in space at speeds approaching thousands of miles per hour.”

Consequently many of the images of Earth we see are actually composites.
This is just the first in a series of images of Earth that will be sent back from a million miles away.
We will soon see the other side, fully illuminated as well.

Links :

• National Geographic : NASA’s ‘Blue Marbles’: Pictures of Earth From 1972 to Today