Observing earth from space

Dr Anjani Ganase, marine biologist and environmentalist, takes us into space for a perspective on Earth, our planet, and our home

This piece is dedicated to Dr Stephen Hawking (1942 - 2018). As a pioneering theoretical physicist and cosmologist, Dr Hawking's work and life exemplified the term - reaching for the stars.

Since the dawn of humankind, we are always looking to the stars for answers. Within this century, we succeeded in sending men and instruments into space to observe and record the cosmos. The satellites that orbit earth either point to the stars collecting information, or point to the earth relaying messages around the planet. It was in 1972, when the crew of the Apollo 17 took a moment to photograph the earth on their way to the moon, sending back the famous photo - not the first of its kind - that referred to the earth as “the blue marble.” Here was the definitive image that showed us our planet dominated by water. This photo of the blue marble displayed the southern tip of Africa surrounded by three oceans – the Atlantic, Indian and Southern oceans. What else did this image reveal? In the top right of the image we see a cyclone hitting the state of Tamil Nadu, India. The south polar ice caps were still visible despite the heavy cloud formation.

The Blue Marble taken from APOLLO 17 in 1972, on its way to the moon.
"We are just an advanced breed of monkeys on a minor planet of a very average star. But we can understand the Universe. That makes us something very special."- Stephen Hawking Image courtesy NASA Johnson Space Center (https://visibleearth.nasa.gov/view.php?id=55418)


While unmanned satellites were being sent out to map the surface of Venus and Mars, observe the radiation of the sun, and whizz past Jupiter on the way out of the solar system, scientists began to see the value of observing earth from this vantage point. Satellites were sent up to record weather patterns in the 1960s (cloud cover, cyclones and atmospheric temperature), and slowly we shifted our gaze to focus on discovering more about earth. Satellites were sent to record both what we can see (visible radiation – photographic images) and what we can’t (heat, infrared, UV and x-ray vision). Today, there are over 1000 satellites orbiting the planet, and some of these are dedicated to continuously recording wind, tropical rainfall, air quality, sea and land temperature, ice sheet changes, vegetation and the changes in the height of ocean’s surfaces. The next time you go stargazing and you see a “star” flying by, it’s most likely a satellite connecting you to the rest of the world or recording the environment around you.

Today we don’t think about satellite launches into space, the data we get from them and how we benefit. The most recognized form of satellite information is through the Google Earth platform. Apart from getting you from A to B, Google Earth has provided the public with massive amounts of visual information on the earth’s landscape, not just of today but dating back to the 1970s, and it is obvious how we’re changing the landscape. You can observe the disappearance of the ice caps in the Arctic, the deforestation of the Amazon rainforest and the expansion of cities along the coastline. These images give scientists a powerful tool to showcase what they have been observing on small scales at globally significant scales. However, this is still a challenge, as these images need to be converted to data for statistical comparisons, something that is time consuming and requires a lot of processing power. 

An example of visible changes in our landscape, quarrying over nine years from 2006 (above) to 2015 (below) near Asa Wright Nature Centre, along the Arima-Blanchisseuse road. Photo Credit: Google Earth, Digital Globe

The sensors that detect heat and other non-visible radiation across the earth tell similar stories – warm surface waters can be tracked across oceans and used predict the severity of coral bleaching on shallow reefs. Other sensors can measure the degree of photosynthesis occurring on the surface of oceans by detecting the green chlorophyll colour. The use of the array of sensors on a satellite might also reveal new discoveries; these have to be validated on the ground to understand what is causing the changes. 

There are places on earth where the satellites cannot record information directly: mainly well below the surface of the ocean, and unfortunately the deep ocean makes up a big portion of the planet. Details about the environment below the surface of the ocean are minimal in comparison to what we know on land. However, through innovative thinking, bathymetry of the oceans can be mapped indirectly by measuring the bulges in the ocean surface that mimic the topography of the ocean floor (NOAA). Unfortunately, other aspects such as the marine ecosystems still need more innovative thinking. 

While the science on human induced climate change has been researched since the 1960s. Satellite information has provided the visual proof, showcasing patterns of an overall warming planet supporting the studies done previously on smaller scales. The most shocking of these observations is the discovery of the clear trends of the retreating ice caps in the Arctic, as well as sea level rise through changes in the earth’s topography using the images recorded over the last 40 years. Satellites highlight the spatial variations that occur across the planet as a result of climate change, showing that the issues related to climate and its changes are complex. 

The data and imagery provided by NASA (National Aeronautics and Space Administration) and NOAA (National Oceanic and Atmospheric Administration) are free for public use. The information is available to show us how Trinidad and Tobago’s landscape and environments have changed over time, and invaluable for us to understand what is stake. We don’t understand what we can lose if we don’t know what’s there. On Tobago’s landscape over the span of ten years, construction and coastal development have increased dramatically in the southeast and along the Atlantic coastline of the island, while the Main Ridge Reserve continues to be intact and not fragmented.

Southwest Tobago in December 2004 (above) and May 2017 (below) showing rapid development over thirteen years. Also note the difference in the vegetation between the wet and dry season. Photo Credit: Google Earth, Digital Globe
In 1977, five years after Apollo 17, the Voyager 1 and 2 satellites were launched to traverse the universe, carrying compact portfolios of humankind’s history. In 1990, as Voyager 1 was about to leave our solar system, Dr Carl Sagan asked that the cameras of the satellite be turned to take one last photograph of the earth. The image recorded was of a  “pale blue dot” the size of a pixel drifting in the vast solar system; then the cameras were turned off to conserve power (over 6 billion km away). This was another reminder that our liveable homes, habitats, ecosystems, environments and their interconnectivity have an upper limit that does not extend beyond the outer atmosphere. The laws of ecology and living ecosystems belong to planet Earth and do not seem to be replicated in the observable universe. So, while we continue to seek other life in the cosmos, we need to ensure that our home - planet, island and ecosystems - is in a healthy enough state to allow us to keep reaching for the stars. 


Earth as a “pale blue dot” in our vast solar system, captured by Voyager 1 in 1990.
“From this distant vantage point, the Earth might not seem of any particular interest. But for us, it's different. Consider again that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives.” - Carl Sagan 1994 - Pale Blue Dot: A Vision of the Human Future in Space  
Photo credit: NASA/JPL (https://photojournal.jpl.nasa.gov/catalog/PIA00452)


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