Mars Orbiters Will Have Front-row Seats to Interstellar Comet
Interstellar comet 3I/ATLAS follows an open-ended, hyperbolic orbit. This view is from above the plane of the solar system and shows the comet entering from the left, passing through the region of the inner planets, and exiting at right. Its orbit is highly eccentric (eccentricity = ~6.3) and inclined 175° to the ecliptic. Being so close to the plane of the solar system, the object will remain within a few degrees of the ecliptic for centuries to come. Credit: JPL HORIZONS with additions by Bob King
The third-known object to have entered our solar system from deep space, the interstellar comet 3I/ATLAS, will never come closer than 240 million kilometers to Earth. And its closest pass to the Sun, when interesting things might happen, comes at a time when it will be hidden behind the sun as seen from Earth.
But on October 3rd, Comet 3I/ATLAS will come about eight times closer than that to Mars. At 30 million km away from the Red Planet, it will come within view of more than a half-dozen cameras and spectrometers on several orbiters, potentially providing us with some of the best views we can hope for of this enigmatic object.
“We are going to try to get images,” confirms Colin Wilson, the European Space Agency (ESA) project scientist for both the Mars Express and ExoMars Trace Gas orbiters. Although the resolution of the two spacecraft’s cameras has no chance of resolving the nucleus, there’s hope for resolving the coma of gases and dust surrounding the central object. That coma may extend a few tens of thousand kilometers across, Wilson says, adding, “We would hope to get maybe several tens of pixels across that.”
Mars Express, Wilson says, will be using the Super Resolution Channel on its High-Resolution Stereo Camera, which is monochromatic. With ExoMars, they will be using the Color and Stereo Surface Imaging System (CASSIS) telescope, which has a 13.5-centimeter primary mirror and four CCDs with different color filters. Both spacecraft carry spectrometers that take in from near-infrared to ultraviolet light. But Wilson cautions, “We don’t know if we’ll get enough signal.”
“So, we are hoping for at least some imagery, and then if we get any spectra, that would be a bonus,” he says. “We are not promising anything other than a monochromatic image.”
(Source: skyandtelescope.org)
