An Alien Wanderer's Close Encounter: Mars Express Captures Interstellar Comet Borisov

Imagine a visitor from another star system, a cosmic wanderer journeying for millennia, making a fleeting pass through our own celestial neighborhood. That's precisely what happened in late 2019, and thanks to the European Space Agency's (ESA) ever-vigilant Mars Express orbiter, we have breathtaking photographic evidence of this historic encounter.

Mars Express, typically focused on uncovering the secrets of the Red Planet, was repurposed for a brief, thrilling moment to act as a celestial paparazzo, capturing stunning images of interstellar comet 2I/Borisov as it sped past Mars.

This wasn't just any comet; 2I/Borisov holds a special place in astronomical history.

It was only the second interstellar object ever detected, following the enigmatic Oumuamua. Its discovery provided scientists with an unprecedented opportunity to study material that originated far beyond our Sun's gravitational influence, offering a direct glimpse into the building blocks of other star systems.

The very thought of an object traveling across the vast expanse between stars is enough to ignite the imagination, and Mars Express was there to witness its grand, albeit distant, flyby.

The critical images were snapped on November 15, 2019, a pivotal moment in the comet's journey through our inner solar system.

At the time, 2I/Borisov was approximately 290 million kilometers (about 180 million miles) from the Sun, while Mars Express itself was about 160 million kilometers (roughly 100 million miles) from the comet. Despite these immense distances, the High Resolution Stereo Camera (HRSC) aboard Mars Express successfully captured the comet's distinctive, fuzzy coma and its ethereal tail trailing behind.

This was no easy feat; the camera, primarily designed for static geological mapping of Mars, had to be precisely angled and tracked to keep pace with the rapidly moving interstellar visitor.

The scientific community buzzed with excitement over these observations. Unlike comets originating from our own Oort cloud or Kuiper belt, 2I/Borisov is believed to be a relatively pristine object, offering a unique chemical fingerprint of the conditions in its home star system.

Its journey through interstellar space means it hasn't been significantly altered by the Sun's radiation or gravity until its recent passage. Studying its composition, tail, and activity provides invaluable clues about the raw materials present in planetary nurseries beyond our own.

After its spectacular, brief performance near Mars, 2I/Borisov continued its journey.

It made its closest approach to the Sun on December 8, 2019, and to Earth on December 28, 2019, before beginning its long, solitary voyage back out into the cold, dark void of interstellar space. The images from Mars Express serve as a powerful reminder of the dynamic, interconnected, and awe-inspiring nature of the cosmos, hinting at the countless other wonders yet to be discovered beyond the confines of our solar system.