The interstellar 3i/Atlas comet is about to have a close encounter with Mars in its hyperbolic trajectory through the internal sun system: on October 3 it will dart at “Solo” 30 million km from the red planet. It will be a unique opportunity that will allow the probes ESA MARS Express and Exomars In orbit around Mars to study this peculiar comet, the third interstellar object Discovered in the Solar System (after 2i/Borisov and 1i/’Oumuamua) showing unique features compared to the native comets of our planetary system. The proximity of the two probes to comet will allow to investigate its shape and chemical composition with a precision impossible from the earth, given that the maximum approach to our planet – scheduled for December 19 – will take place at a distance of Ben 269 million km.
After October 3, the comet will continue its journey to 58 million kilometers from Venus on 7 November and 46 million km from Jupiter on March 16, 2026, where he will be further studied by the European probe Juice before abandoning our stellar system forever. In these days 3i/Atlas is hardly visible from the earth because of the reduced angular distance from the sun and its glow; In the next few days he will stop being visible and we will be able to return to observe it from the end of November, when he “re -emerges” from behind the album of our star.
Because the close passage of Mars is important: what we will study
On October 3, the interstellate 3i/Atlas comet will be only 30 million km from Mars. Near the close passage to the red planet, ESA has planned to address the scientific tools of the Mars Express and Exomars probes, generally used to study the surface of Mars, towards the interstellar comet. The tools High Resolution Stereo Camera (Hrsc) of Mars Express e Color and Stereo Surface Imaging System (Cassis) of Exomars will be used to obtain Detailed images of the hair and tail of the comet. The goal is to determine the degree of cometsthat is, the rate of loss of gas and dust in approaching the sun, andexact size and shape of the 3I/Atlas nucleus through the modeling of the hair (the actual nucleus is too small to be able to be observed directly from the instruments of Mars Express and Exomars).
The size of this comet, in particular, are at the center of a recent astrophysicist article Avi Loebwhich considers the “too large” comet (at least 5 km) to be only the third interstellar object discovered in the sun system. Loeb even goes to use this statistical anomaly to consider the hypothesis that in reality the object is not a comet but an alien technology, even if it is a very problematic idea from a methodological point of view.
In addition to these photos of a photometric nature, the spectrographers Omega and Spicam of Mars Express and Nomad of Exomars are also used. The goal is to investigate the chemical composition of the cometin search of the spectral signatures of compounds such as water, carbon dioxide, carbon monoxide, or carbon -based molecules and nitrogen. Determine which compounds are present on the comet and in what relative percentage allows you to compare 3i/Atlas with the other comets of the Solar System and therefore understand if the cometary compositions are “universal” or depend on the star system in which they have formed.
What we know about 3i/Atlas
3i/Atlas is the third interstellar object Discovered in the Solar System after 2i/Borisov and 1i/’Oumuamua. The discovery took place on 1 July 2025 thanks to the observations of the telescope ASTEROID Terrestrial-Impact Last Alert System (Atlas) Telescope in Chile. His unusual hyperbolic trajectory with high eccentricity immediately revealed the interstellar nature of the objectthat is, formed in a stellar system outside the sun system. The observations conducted with telescopes from the ground and in space, such as space telescopes Hubble and James Webb, managed to immortalize one hair around 3i/Atlas and a hint of tailcreating consent in the astronomical community about the nature cometary of the object, although with peculiar characteristics that distinguish it from the comets of the Solar System.
3i/Atlas is darting in the solar system at the incredible speed of 210,000 km/h, with an almost parallel trajectory to the plane of the ecliptic that will lead her to reach maximum proximity to the sun on 29 October (200 million km), while the maximum approach to the Earth will take place on December 19 at 269 million km. The interstellar comet will also carry out close encounters with Venus on 7 November (58 million km) and with Jupiter on March 16, 2026 (46 million km). These numerous close encounters are one of the reasons that initially Avi Loeb to speculate on “alien” nature of the objectan idea decidedly rejected by the international scientific community.
