For the first time ever, the European Space Agency (ESA) is preparing to launch a multi spacecraft mission to intercept a truly pristine comet, one that has never entered the inner solar system nor has been irrevocably changed by the Sun’s heat.
With participation from the Japanese Space Agency (JAXA) and partners like Estonia’s Tartu Observatory, the crux of the mission —- due for launch in 2029 —- is to remotely characterize the building blocks of our earliest solar system.
An estimated 500-million-euro mission, Comet Interceptor will consist of three spacecraft launched together atop the same rocket payload, says ESA. The spacecraft will simultaneously conduct observations from multiple points around the target comet, creating a 3D profile of a ‘dynamically new’ long period comet, ESA notes.
Why Is This Mission So Unique?
The comets studied up close thus far have been so heavily modified that it is difficult to say anything concrete about them, Mihkel Pajusalu, a planetary scientist at Estonia’s Tartu Observatory, told me in his office.
The idea here, says ESA, is to study a comet that contains unprocessed material dating from the dawn of our solar system.
Although amateur astronomers love the light shows that the Sun provides when comets pass by our own star, astrobiologists need to understand the distribution and building blocks of our early protoplanetary disk to understand how our solar system evolved.
To that end, planetary scientists at Estonia’s Tartu Observatory are playing a vital role. They are building the estimated 5-million-euro Optical Periscopic Imager for Comets (OPIC) which, among other things, will characterize gases from the target comet’s nucleus.
Previous cometary missions have studied comets that have flown past the Sun several times, which means that they have lost a lot of their surface materials, says Pajusalu. They would be pretty much unrecognizable compared to what they used to be when they formed, he says.
The Comet Interceptor will likely launch before it even has a cometary target. But once it arrives at the gravitationally-stable Earth-Sun Lagrange Point 2, it is prepared to remain there waiting for the right opportunity to intercept a long-period comet.
The current official baseline is up to three years to wait before the mission makes its interplanetary trek to intercept the comet, says Pajusalu.
OPIC is named in honor of Estonian astronomer Ernst Öpik (who along with Dutch astronomer Jan Oort) proposed that there is a massive reservoir of comets lying on the outermost fringes of our solar system, now known as the Öpik-Oort Cloud. It’s from this reservoir of comets that the science target for the Comet Interceptor mission will originate.
OPIC’s goal is to map the target comet’s nucleus, says ESA. The hope is that the mission can observe the comet’s dust jets at visible and infrared wavelengths using an autonomous camera pointed to the side of the spacecraft, ESA notes.
The camera will operate perpendicular to the spacecraft’s direction of flight using a folding mirror similar to a periscope. The point of having a camera with a periscopic mount is so that particles from the comet won’t hit the instrument’s glass optics during the spacecraft’s closest approach of only some 400 km.
Basically, it’s like a submarine periscope, says Pajusalu.
But How Difficult Will It Be To Identify The Right Target?
Comet Interceptor’s target identification workgroup is already working on it, but this will be a very difficult process, says Pajusalu. The biggest hopes are on the new Vera Rubin Observatory in Chile which should allow the detection of objects earlier than currently possible, he says. Since the objects will be faint, many observations will be required to determine the trajectories of the objects well enough to understand if interception is possible, says Pajusalu.
What Is Potentially Most Significant About OPIC’s Observations?
Mapping the surface and inner coma (the nebula of gas and dust around the nucleus) of a pristine object entering the inner Solar system for the first time, says Pajusalu. OPIC’s observations will be processed together with data from other instruments to form a comprehensive 3D model of the target and its near environment, he says.
Why is this mission important to astrobiology?
We will get a better estimation of conditions at the beginning of the solar system to know what the chemical composition was early in its history, says Pajusalu. This will give us a better understanding of what was present in the early solar system before life emerged, he says.
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