ESA’s Rosetta Spacecraft Spots A ‘Baby Bow Shock’ Forming Around Famous Comet 67P


Two years after the Rosetta mission came to an epic end, the European Space Agency (ESA) has unveiled some thrilling news about its 12-year-long mission to study Comet 67P/Churyumov-Gerasimenko.

As it turns out — despite original indications to the contrary — the Rosetta spacecraft didn’t miss its chance of witnessing a bow shock at Comet 67P. The probe was actually successful at spotting one in the process of being born around the 2.5-mile-wide comet, the space agency announced earlier today.

Given that Rosetta was initially believed to have come up empty-handed in this particular respect, the revelation is understandably exhilarating. Moreover, this newly revealed detection is actually the first time that a bow shock in such an early stage of formation has ever been seen anywhere in the solar system, stated ESA officials.

What Is A Bow Shock?

All the celestial bodies in our solar system — planets, comets, and asteroids included — float around in a sea of cosmic plasma emanating from the sun. Also known as the solar wind, this gaseous bubble filled with charged particles encompasses the solar system in all its entirety, continuously flowing around and toward the objects that populate it.

“As the supersonic solar wind flows past objects in its path, such as planets or smaller bodies, it first hits a boundary known as a bow shock. As the name suggests, this phenomenon is somewhat like the wave that forms around the bow of a ship as it cuts through choppy water.”

The Rosetta Mission

The Rosetta spacecraft studied Comet 67P for a period of two years, from August 6, 2014, until September 30, 2016 — when it (intentionally) crash-landed on the comet that it had spent a decade chasing through the inner solar system.

As the Inquisitr previously reported, the European probe was the first to ever orbit and touch down on a comet in space. On November 12, 2014, the spacecraft deployed its Philae lander on the comet’s surface, setting the record as the first mission to succeed a soft landing on a cometary body.

“Comet 67P/Churyumov-Gerasimenko made history as the first comet to be orbited and landed upon by robots from Earth,” notes NASA.

Comet 67P/Churyumov-Gerasimenko imaged by the Rosetta probe on January 31, 2015.
Composite image of Comet 67P/Churyumov-Gerasimenko, photographed by the Rosetta probe on January 31, 2015.Featured image credit: ESA/Rosetta/NAVCAMNASA/CC BY-SA IGO 3.0

‘Baby Bow Shock’ At Comet 67P

According to a recent analysis of the Rosetta data, the spacecraft encountered the “baby bow shock” around Comet 67P on March 7, 2015 — exactly seven months into its mission at the now-famous comet. The detection was made by the Rosetta Plasma Consortium — a series of instruments on board the space probe, made up of five different sensors designed to examine the plasma around the comet.

At the time, the spacecraft was flying toward the sun in hot pursuit of the comet. About a year later, on February 24, 2016 — when both the probe and its target were returning from their trip around the sun — the instruments picked up the signal again.

The exciting results were published last month in the journal Astronomy & Astrophysics, along with a computer simulation that reconstructs the big encounter.

“The bow shock is the first boundary the solar wind encounters as it approaches planets or comets. The Rosetta spacecraft was able to observe the formation of a bow shock by following Comet 67P/Churyumov-Gerasimenko toward the sun, through perihelion, and back outward again,” the authors wrote in their paper.

Since the Rosetta probe sighted the forming bow shock as the boundary changed position due to the influence of the comet’s magnetic field, the spacecraft found itself alternatively outside of the shock and behind it. The phenomenon is illustrated in the photo below, with the two frames showing the dual position of the probe relative to the comet’s bow shock.

Outside view (left) and inside view (right) of the bow shock spotted by Rosetta around Comet 67P.Featured image credit: ESA

The interesting thing about this detection is that the bow shock was actually sighted a lot closer to the comet’s nucleus than expected.

“We eventually spotted it around 50 times closer to the comet’s nucleus than anticipated in the case of 67P. It also moved in ways we didn’t expect, which is why we initially missed it,” said Herbert Gunell, one of the two scientists who led the study. The researcher is affiliated with both the Royal Belgian Institute for Space Aeronomy in Belgium and Umea University in Sweden.

According to Matt Taylor, a Rosetta project scientist at the ESA, this detection of a “baby bow shock” is one-of-a-kind.

“These observations are the first of a bow shock before it fully forms, and are unique in being gathered on-location at the comet and shock itself.”