Some space images ask you to zoom in. NASA’s Astronomy Picture of the Day for 17 October asks you to put on red-and-blue glasses and look around a comet.
The subject is 67P/Churyumov-Gerasimenko, the oddly shaped world visited by Europe’s Rosetta mission. Its two connected lobes can suggest a rubber duck, although the surface is all rugged terrain rather than something you would want in the bath.
The feature is new; the photographs are not. They were taken in July 2015, when Rosetta was close enough to turn a distant point of light into a landscape. Combining two views gives that old encounter another dimension.
The pictures were taken 184 kilometres away
The featured stereo view uses two images captured by Rosetta’s OSIRIS narrow-angle camera on 25 July 2015. The spacecraft was about 184 kilometres from the comet, according to the APOD description.
That is a very different perspective from watching a comet as a streak in the sky. The larger lobe of the nucleus measures roughly four kilometres across, while the smaller is about 2.5 kilometres. A narrow neck connects them.
At this scale, the nucleus becomes a place with shape, relief and uneven surfaces. The two-lobed outline is only the beginning. In the featured view, jets rise from an active comet nearing its closest approach to the Sun.
Those jets are part of what makes the scene so striking. A comet can look solid and rocky at close range while releasing material into space. The familiar bright head and tail seen from far away come from activity around a much smaller central body.
Why the red and blue edges look strange
The picture is an anaglyph: two slightly different views are combined using different colours. The coloured lenses help send the appropriate view to each eye, allowing the pair to be perceived with depth.
Without the glasses, the displaced coloured edges can look like an editing error. They are doing a job. The feature is designed for stereo viewing rather than simply adding a fashionable colour treatment to a space photograph.
NASA’s separate classroom guide describes making basic glasses with sturdy card and red and blue acetate. In its arrangement, the red filter goes over the left eye and the blue over the right. Keeping the viewing area clear of tape helps preserve the view.
That guide is an older educational resource, rather than a newly announced mission product. It provides a straightforward way to understand the sort of glasses the comet feature calls for. An ordinary pair of sunglasses does not perform the same colour-separation task.
A comet’s head is much bigger than its nucleus
NASA describes comets as bodies made of frozen gases, rock and dust. When they are frozen and far from the Sun, the central body can be on the scale of a small town.
As a comet approaches the Sun, heating releases gas and dust. The surrounding glowing head can become larger than a planet, with a tail stretching millions of miles away from the Sun.
That is why the measurements in a close-up can feel unexpectedly small. A four-kilometre lobe and an enormous visible comet are not contradictory descriptions. One refers to the solid nucleus; the other includes material spread around and behind it.
The scene also needs a different mental picture from a rock burning like a meteor in the atmosphere. Rosetta was following a comet through space. The activity described in the feature comes from its approach to the Sun, rather than atmospheric entry above Earth.
Rosetta stayed for the changing seasons
Rosetta launched on 2 March 2004. The European Space Agency mission carried both an orbiter and a lander, Philae, with NASA providing instruments and other support.
In August 2014, Rosetta became the first spacecraft to orbit a comet. On 12 November that year, Philae landed on 67P and began sending back images and data. NASA’s mission summary describes 20 science instruments across the two spacecraft.
The purpose was sustained study, rather than a quick flyby photograph. The mission accompanied the comet on its journey towards the inner solar system and back out again, allowing researchers to observe a changing target.
The July 2015 images belong to that period of close observation. Knowing the date helps separate what the image shows from what NASA is doing today. There is no new spacecraft arriving at 67P in this announcement.
Rosetta’s mission ended on 30 September 2016 with a controlled impact on the comet’s surface. The spacecraft’s operations stopped, but the archive it helped create remains available for scientists and the public to explore.
This comet does not cross Earth’s orbit
NASA’s overview places 67P in the Jupiter-family group of comets. Its path crosses the orbits of Jupiter and Mars, approaching but not reaching Earth’s orbit.
The agency says such comets are thought to have come from the Kuiper Belt beyond Neptune, with collisions or gravitational interactions altering their paths. That is background about their likely history, rather than something the new stereo picture alone demonstrates.
It is another reason to resist treating an impressive close-up as an incoming-object warning. The current feature is an invitation to examine an archived landscape, not an alert that the comet is approaching Malaysia or threatening Earth.
There is far more than one angle to explore
APOD points readers to a catalogue containing nearly 1,400 anaglyphs from the mission. The featured processing is credited to Philippe Lamy and colleagues, using Rosetta’s OSIRIS imagery.
A large archive offers something one famous image cannot: opportunities to compare different views instead of remembering only the duck-like silhouette. The shape catches your attention; the changing angles reward a closer look.
If you try the featured image, start with the dated original in NASA’s source page and the appropriate glasses. Our cover is a newly generated conceptual illustration, not a stereo image. The real depth experiment belongs to those two spacecraft photographs, taken more than a decade ago and still capable of making a familiar comet feel surprisingly close.
Sources & further reading
Prepared with AI assistance from linked reporting. The cover is an AI-generated editorial illustration. Spotted something we should correct?