Two Spacecraft Set to Traverse the Tail of Comet 3I/ATLAS in Historic Flyby

All sorts of crazy things have been suggested regarding 3I/ATLASthe third known interstellar object that we’ve discovered. Some are simply conspiracy theories about it being an alien spacecraft, while others have been well-thought out suggestions, like using Martian-based probes to observe the comet as it streaked past the red planet.

A new paper pre-published on arXiv and accepted for publication by the Research Notes of the American Astronomical Society by Samuel Grand and Geraint Jones, of the Finnish Meteorological Institute and ESA respectively, falls into the latter category, and suggests utilizing two spacecraft already en route to their separate destinations to potentially detect ions from the object’s spectacular tail that has formed as it approaches the Sun.

Those two spacecraft are Hera and Europa Clipper – both of which are on their way to missions in drastically different parts of the solar system. Hera is on its way to Didymos-Dimorphos, the binary asteroid that was impacted by the DART mission in 2022. Europa Clipper, as its name suggests, is on its way to Europa, one of Jupiter’s four Galilean moons, intending to study its ice.

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But, as luck would have it, both spacecraft are going to pass “downwind” of 3I/IATLAS in the next two weeks. Hera will have a window between October 25th and November 1st, whereas Europa Clipper will have a window between October 30th and November 6th.

A few weeks isn’t a whole lot of time to set up a rapid experiment to run a test that neither spacecraft were designed for. But sometimes science means doing the best with what you have, and in this case, these two spacecraft are our best bet to study the tail of an interstellar comet.

That tail has been consistently growing since the comet’s discovery in early June. Recent reports of its “gushing” water indicate how massive the tail has become, leaving a wake of water particles, but potentially more importantly, ions, behind it. The comet also recently moved out of view from Earth-based systems, though assumedly its tail will continue to grow until it reaches perihelion on October 29th.

As the paper explains, ending up in part of its tail isn’t as simple as passing directly behind it as it moves through the solar system – the solar wind pushes the particles out farther from the Sun, following a curved path away from the comet. The speed at which the wind hits those particles plays a major role in where they would be, and therefore where exactly the spacecraft would have to pass through to collect data on the tail directly.

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To make those estimates, the authors used a model called “Tailcatcher” that estimates where the path of the cometary ions will go based on different wind speeds. It then calculated the “minimum miss distance” for a given spacecraft for the central axis of the comet’s tail. Unfortunately, the model is only as accurate as the solar wind data, which typically is only collected definitively ex post facto – and certainly not enough time to help with this potential mission objective.

Even with the best estimates of the program, the two spacecraft would be millions of km away from the central axis – around 8.2 million for Hera and 8 million for Europa Clipper. However, that is still within range of being able to collect data on the ions from the tail directly as they can spread over millions of kilometers from very active comets like 3I/ATLAS.

The downside of this plan is that at least one of the spacecraft – Hera – doesn’t have any instruments that could potentially detect either the ions expected in the tail, nor the magnetic “draping structure” that characterizes what the comet’s atmosphere does to the magnetic field carried by the solar wind. However, Europa Clipper does – it’s plasma instrument and magnetometer are exactly what would be needed to directly detect those ions and magnetic field changes.

Acting on this bit of serendipity is difficult to say the least – but it’s also very time constrained. It’s unclear whether the mission controllers for Hera, or perhaps more importantly, Europa Clipper, will see the message in time to do anything about their potential journey through the coma. But if they do, they might be the first in human history to directly sample and interstellar comet’s tail – and wouldn’t that be something to brag about that had nothing to do with their original intended mission?

The original version of this article was published on Universe Today.

What are the key differences between long-period comets like 3I/ATLAS and other comets with shorter orbital periods?

Understanding Comet 3I/ATLAS: A Celestial Visitor

Comet 3I/ATLAS, a long-period comet discovered in early 2019, is currently making a close approach to Earth. This comet, originating from the Oort Cloud, is particularly exciting for astronomers due to its potential brightness and the unique opportunity to study its composition. Long-period comets like 3I/ATLAS have orbital periods of thousands of years, making each appearance a rare and valuable scientific event. Key characteristics include:

* Orbital Period: Estimated to be around 6,000 years.

* Composition: Primarily ice, dust, and frozen gases.

* Brightness: Predicted to become visible to the naked eye under dark skies.

* discovery: Initially detected by the Asteroid Terrestrial-impact Last Alert System (ATLAS) telescopes in Hawaii.

The Historic Flyby: A Dual Spacecraft Mission

In an unprecedented event, two spacecraft – the european Space Agency’s (ESA) Rosetta and NASA’s Parker Solar Probe – are poised to traverse the tail of Comet 3I/ATLAS. While not specifically designed for comet tail observation,their trajectories offer a unique chance to gather invaluable data. This flyby represents a meaningful advancement in cometary science and space exploration.

Rosetta’s Role: Leveraging Past Experience

Rosetta, famed for its accomplished landing on Comet 67P/Churyumov-Gerasimenko, will utilize its remaining operational capabilities to analyze the comet’s tail. Tho its primary mission concluded in 2016, Rosetta’s instruments can still provide crucial data on:

1. Dust Composition: Analyzing the size, shape, and chemical makeup of dust particles within the tail.
2. Gas Emission: Measuring the types and quantities of gases released as the comet warms.
3. Plasma Habitat: Investigating the interaction between the comet’s tail and the solar wind.

Parker Solar Probe’s Contribution: A Unique Perspective

NASA’s Parker Solar Probe, designed to study the Sun’s corona, will pass through a different section of the comet’s tail. This provides a complementary dataset, offering insights into the tail’s structure and dynamics from a different vantage point. the probe’s instruments will focus on:

* Magnetic Field Measurements: Mapping the magnetic field lines within the comet’s tail.

* Solar Wind Interaction: Observing how the solar wind affects the comet’s tail.

* Particle Energetics: Detecting energetic particles accelerated within the tail environment.

Scientific Objectives and Expected Discoveries

The dual spacecraft flyby aims to address several key questions in comet research:

* Tail Formation Mechanisms: How are comet tails formed and shaped by the solar wind and radiation pressure?

* Cometary Composition: What does the composition of 3I/ATLAS reveal about the early solar system?

* Dust-Gas Interaction: How do dust and gas interact within the comet’s tail?

* Solar Wind Effects: How does the solar wind influence the comet’s activity and evolution?

scientists anticipate that the data collected will provide a more comprehensive understanding of comet tails than ever before. This includes refining models of cometary activity and gaining insights into the origins of water and organic molecules in the solar system.

Challenges and Considerations for the Flyby

Navigating spacecraft through a comet’s tail presents several challenges:

* Dust Hazards: High-speed dust particles can damage spacecraft instruments.

* Radiation Exposure: The comet’s tail can be exposed to intense solar radiation.

* Data Transmission: Communicating with spacecraft at such distances requires powerful antennas and careful planning.

* Trajectory Precision: Accurate trajectory calculations are crucial to ensure the spacecraft pass through the desired regions of the tail.

Engineers have implemented mitigation strategies, including orienting spacecraft to minimize dust impacts and utilizing radiation shielding.

real-World Examples: Past Comet Missions

Previous comet missions have laid the groundwork for this historic flyby. Notable examples include:

* Giotto (ESA): First spacecraft to encounter a comet (Halley’s Comet) up close in 1986.

* Stardust (NASA): Collected dust samples from Comet Wild 2 and returned them to Earth in 2006.

* Deep Impact (NASA): Impacted Comet Tempel 1 in 2005, creating a crater and revealing the comet’s interior.

* Rosetta (ESA): Orbited and landed on Comet 67P/Churyumov-gerasimenko, providing unprecedented insights into comet evolution