A pale blue dot and a few other thoughts

By Joyel K Pious

A story of a princess comes up effortlessly when I try to recollect my earliest brushes with the realm of fantasy. I read the children’s novel Nakshatra Kannulla Rajakumari (Princess with starry eyes) in a Malayalam-language magazine during my primary school days. Except for the gist ─ A princess from a faraway planet arrives on Earth and makes friends with a gang of children who help her hide from powerful alien foes ─ I have forgotten everything else about it. The story made an impression though, seeding the idea that there could be worlds beyond the sky. In the years that followed, I would come across facts that sounded more like fantasy and were spiced up with sketches and photographs, firing up my imagination about space travel. Some of the photos that blew my mind those days had been captured by a pair of small spacecraft launched a decade before I was conceived.

A pixel becomes science, art, and philosophy

Shot off into deep space in a gap of a few weeks in 1977, albeit in different directions, Voyager 1 and Voyager 2 hold the record for being the fastest and farthest human-made objects. Currently pacing through the interstellar region that separates our solar system from the rest of the Milky Way galaxy, the Voyagers have had close encounters with our planetary neighbours, providing us with the first close-ups of those strange worlds. Among the hundreds of images the Voyagers took, the most iconic is a grainy photograph known by the title ‘The Pale Blue Dot’. Captured by Voyager 1 in 1990, more than a decade into its lonely journey, this is the most distant view of our planet ever photographed. As its title indicates, the image shows the Earth as, according to the legendary 20th-century scientist Carl Sagan, “a mote of dust suspended in a sunbeam”.

‘The Pale Blue Dot’ was not an accidental photograph but a result of years of lobbying, planning and meticulous execution. As Voyager 1 darted past Mars, Jupiter, Saturn, Uranus and Neptune towards the dark interstellar space, the photography goals of the spacecraft were over. The mission scientists were eager to turn off the two onboard cameras, for the power reserve of the spacecraft was depleting. Sagan was one of the few scientists in the Voyager team, who wanted the spacecraft’s wide-angle camera to turn backwards and shoot a panorama of the world it was leaving behind. The plan was risky because turning the now-primitive vidicon camera ─ a version of the older television camera that converts light into electric signals ─ backwards (towards the Sun) could damage its highly sensitive photoinductive apparatus made for capturing images of faint objects. Moreover, the exercise needed a precise manoeuvre of the spacecraft, fleeting at a distance of more than 5 billion km. Despite intense initial opposition from a section of the Nasa administration, Sagan succeeded in convincing them. Subsequently, special codes were created and transmitted to Voyager 1, which woke up its wide-angle camera drowsing in the unearthly freeze. The Earth was shot on February 14, 1990, just 34 minutes before the cameras were switched off forever^[1]. Available on the Nasa website for free download, ‘The Pale Blue Dot’ is likely to look insignificant and unphotogenic to an uninformed eye.

Like any other photograph, this, too, was created by a machine, but after being imagined for years in advance by scientists. It was also a result of human curiosity to look at ourselves from such a colossal distance. To get a perspective, the sunlight reflected from the Earth travelled several billion kilometres to reach the imaging system of Voyager 1, which converted it into signals and transmitted it back to us. What we see in the photograph is a strange mirror image of ourselves. Unsurprisingly, the image’s scientific uses were limited. Being the farthest view of the Earth ever captured, it, however, kicked up several discussions. First of all, the debate, about whether a photograph without any ‘scientific value’ was worth risking such a unique exploratory mission, was muted by the profound role that the image played in inspiring future scientists, artists and philosophers. From the belief that they were the focus and purpose of the creation, humans have progressively come to realise that they are occupying only a pixel-sized space in the universe. The grainy image captured by Voyager 1 is a visual testament to that insignificance.

A yellow view through acidic clouds

Despite their looming insignificance in the grand scheme of things, humans never stopped themselves from exploring the unknown. The knowledge from such pursuits tells us that the Earth is a rare haven of life in the vastness of space. This realisation started growing in us in the early decades of space explorations, especially with the visits of unmanned Soviet spacecraft to Venus. Being the third brightest object in our sky, after the Sun and the Moon, Venus has long been associated with our myths and cultures. Also known as ‘Morning Star’, the planet shares several identical qualities with the Earth, creating an illusion that it also harbours oceans and life. The USSR’s Venera missions, beginning in the 1960s, however, relayed us back data, photos and sounds that busted this belief, proving that the planet, named after the Roman goddess of love, is a yellow world with sulfuric acid clouds and hot and dense carbon dioxide – hostile even to the thick titanium-hulled Venera spacecraft. Photographing such a planet would prove to be a herculean task. In fact, photography was not an objective in the first few Venera missions.

When the Venus exploration was in its infancy, there was no room for photography equipment in the tiny and cramped spacecraft. And the focus was more on collecting data. With the Cold War between the US and the USSR triggering a space race, both powers increasingly wanted to showcase their achievements to the world. What could this job better than photographs? Even though the Veneras started flying in the early 1960s, cameras were installed on them only a decade later. Considered one of the greatest feats of Soviet imaging capabilities, the Venera 9 spacecraft in 1975 relayed back a single black and white image of the Venusian surface ─ the first-ever photograph taken from the surface of another planet. Seven years later, in 1982, Venera 13 sent back the first colour image of the planet’s surface, besides recording sounds from there, another first in the history of space exploration.

It is often said that scientific advancement is a byproduct of challenges. In that sense, remote planetary photography leapt with Venera 9 and the subsequent missions, thanks to the highly hostile atmosphere of Venus. To bring some perspective, consider these facts. Any spacecraft entering the planet has to pass through its thick and acidic clouds. If it manages to land, the surface is an unwelcoming furnace with a temperature of around 500 degrees Celsius and a pressure 92 times stronger than that of Earth’s. There was no lens or imaging system capable of withstanding such extreme temperature and pressure. The maximum life duration of a spacecraft on the surface was just 127 minutes in the entire Venera programme, making the capture, processing and transmission of images a tricky affair.

To photograph such an alien territory, the Soviet space agency used an improvised periscope arrangement, the thick metal caps of which would blow out immediately after the spacecraft landed on the planet, to direct the light towards the camera which was protected inside the hull. The imaging system was a facsimile camera, which contained a telephotometer, a now obsolete system of taking pictures remotely, with a 360-degree field view. Such cameras provided better geometric fidelity (accuracy of shape) than a vidicon system, more picture elements per frame, ability to take single frame panoramic pictures, a very high contrast ratio within a picture, a choice of multiple spectral responses over a wide range, image transmission over a low bit-rate communications channel without storage, need for very low power, small size, low weight, and the option to make it rugged to meet flight requirements ^[2]. Compared to the US scientists, the Soviets improvised such cameras to a great extent.

The first B&W picture from Venus was about 115 x 512 pixels. Technologies such as automatic gain control and logarithmic quantisation were used to handle the unknown dynamic range of illumination on the alien planet. The colour image from Venera 13 was the result of red, green and blue filters on the camera. The prominence of yellow in the photograph gives an eerie feeling about the Venusian world, justifying the scientific data about its hostile atmosphere. The yellowness is the result of the planet’s carbon dioxide-rich atmosphere and thick acid cloud blocking out a large part of the solar light, including shades of blue – a stark contrast with our bluish sky. The Venera images, a result of several failures and ingenuity, remind us of the uniqueness of our own home and the need to respect its fragile atmosphere, which is witnessing a carbon dioxide build-up due to our reckless actions.

A bluish sunset on red planet

Even as the Venusian images compel us to acknowledge the Earth’s unique position in the solar system, the fragility of life here, compounded by fears of nuclear war, climate catastrophe and meteorite strike, has led a section of humanity to fantasise a second home. Our planetary neighbour Mars comes into the picture in this background. With its red hue visible even to the naked eye on a starry night, Mars has always been an object of fascination. It is no wonder then that we look upon the ‘Red Planet’ as a possible location of future human colonies. While the exploration of Mars gained momentum during the Cold War, our interest in the planet never waned, with new entrants such as China, European Union, India, Japan and the UAE sending spacecraft to the planet in the last three decades. Since Mars is the most photographed planet after the Earth, there is no dearth of images from its surface, despite the high rate of failures of missions to the planet. The quality of Martian photographs has progressively improved, making many of us imagine that the iron-rich planet holds the key to the human race’s destiny. Among the hundreds of pictures taken from Mars, I would like to present one here.

Taken by Nasa’s robotic rover Spirit in 2005, it is a view of the Sun setting below the Gusev crater on Mars. Shot as a panoramic camera mosaic, the image was captured by the rover on its 489th day (called ‘sol’) on the Red Planet ─ Compare this period with the barely two hours that a Venera probe could endure in Venus. The sunset in the western sky of Mars was shot using three colour filters ─ 750-nanometer, 530-nanometer and 430-nanometer ─ on the rover’s camera. This combination of filters produces false colour images, similar to what a human would see. How real is this picture, if we imagine ourselves to be on that alien planet at that time? The bluish glow would look the same but the redness of the sky farther from the sunset would be much fainter ^[3]. The contrasting resolution, complemented by hidden details of the terrain, makes it hard to differentiate this image from a landscape photograph taken from the Earth. If there is no title or textual information, only a careful viewer, who will notice the strange bluishness of the sunset, might be able to tell that it is an unearthly scene. Another information that can be gathered from this image is the apparent size of the Sun on the Red Planet. Compared to the Earth, Mars is away from the Sun and hence, the setting Sun will look only about two-thirds the size when we compare it to a sunset on the Earth.

More than just a landscape shot, the image holds interesting scientific information. According to Nasa, scientists occasionally take sunset and twilight images of the planet to determine “how high into the atmosphere the Martian dust extends, and to look for dust or ice clouds”. Also, photographs of Martian sunrise and sunset show the twilight glow remains visible for up to two hours before sunrise or after sunset. Such a long twilight is caused by the scattering of sunlight by a large amount of high-altitude dust. Dust being a key feature of the planet, any future plan to settle there will have to take into account the effects of the dust on man and machine. Even as we imagine a future on the dusty planet, there is an unprecedented image-making mission in progress; its goal is to peep through the thick clouds of cosmic dust and dig out pictures of our past.

An image from a cosmic time machine

Time travel has probably been a fantasy since the very beginning of human civilisation, even though it remains only a dream in comparison to the fantasy of flying. However, by making use of a peculiar character of light we can look into our past. Called ‘red shift’, this is a phenomenon where a ray of light, any electromagnetic radiation for that matter, undergoes a steady increase in its wavelength as it travels through time and space. The longer the duration of travel, the higher the shift in wavelength, towards the infrared side of the spectrum of radiations. This means that to see the past of our universe, one has to look for the infrared radiations from distant corners.
Largely a visual animal, humans want to see things to believe in them, there are exceptions though. But our capacity to see is restricted to a very narrow band of light called the visible spectrum. Whatever falls outside this band is invisible to us. It also means that there are more things out there that we can’t see, including the red-shifted light coming from the distant past. Capturing this unseen light and converting it into visible photographs is currently one of the most exciting activities in astronomy. And it is being done with the help of a state-of-the-art space telescope carrying powerful infrared cameras.

The James Webb Space Telescope (JWST), a collaboration of Nasa, the European Space Agency, and the Canadian Space Agency, is a multi-billion-dollar machine designed to look deeper and farther than any telescope ever invented by us. Launched into an orbit far away from the Earth and the Sun, and facing towards the dark interstellar space, it has been relaying back images hitherto unimaginable. To give a perspective of the truly remarkable nature of this image-making system, I am using the first photograph created out of the JWST data. Titled ‘Webb’s First Deep Field’, this photograph was unveiled by US President Joe Biden in 2022.

The “deepest” and “sharpest” photograph of the universe so far, it shows a galaxy cluster named SMACS 0723 containing thousands of galaxies. The image also contains the “faintest objects ever observed in the infrared”, proving the telescope’s sensitivity to see even the faintest, here also meaning the oldest light. How is such a photograph created? In fact, it is not a single photo but a composite of images taken at different infrared wavelengths, with a total exposure time of around 12.5 hours. In the process, the telescope’s sensors picked up light rays that had started their journey 4.6 billion years ago, helping us look back in time within a billion years after the Big Bang. While the original data sent by the JWST pertains to a series of black-and-white images, the final composite picture is created by scientists after colouring the individual pictures based on the corresponding infrared wavelength. Colouring is necessary to study the features of various objects in the photo as well as for aesthetic purposes.

Watching this photo, one may feel it is a wide-angle view, but the angle of view is as “tiny as a grain of sand held at an arm’s length” ^[4]; a part of the universe almost comparable to the size of the grainy dot-sized image of the Earth captured by Voyager 1 three decades back. If such a pixel-sized angle reveals such a crowd of galaxies, each containing millions of stars and planets, what will be the actual size of the universe? How alone are we in such a crowded world? Like the childhood story, are there any alien princesses hiding in the blackness the Webb is staring into? We may never know. But fantasies never die, and the quest never ends.

Post-script



The images discussed in this article are not the most visually striking among the photographs taken by remote spacecraft over the last six decades. An uninformed person might view them without any sense of ‘awe’. Like the debates on beauty, aesthetics and value in art, these four pictures also raise similar questions. Moreover, all of them were captured by machines obeying the commands fed to them in advance. There were no real-time instructions to shoot this or that. All these images are in the public domain and available for free, making them a part of our collective knowledge bank. These photographs assume an artistic value due to their historical, philosophical and scientific importance rather than visual appeal.

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References

[1]  Pale blue dot: A vision of the human future in space, Carl Sagan, Ballantine Books

[2] https://ntrs.nasa.gov/api/citations/19720003193/downloads/19720003193.pdf

[3] Sunset Mars

[4] Nasa’s Webb Delivers Deepest Infrared Image of the Universe