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The Feasibility of a Spacecraft Flyby with the Third Interstellar Object 3I/ATLAS from Earth or Mars

Atsuhiro Yaginuma, Tessa Frincke, Darryl Z. Seligman, Kathleen Mandt, Daniella N. DellaGiustina, Eloy Peña-Asensio, Aster G. Taylor, Michael C. Nolan

TL;DR

This work addresses the feasibility of a spacecraft flyby of the interstellar object 3I/ATLAS using near-Earth or Mars-based assets. It develops a universal-variable Lambert-based framework to compute minimum-energy, direct-transfer trajectories, mapping the required $\Delta V$, $C_3$, flyby velocity, and phase angle across launch windows and documenting how discovery timing constrains practicality. The key finding is that post-discovery Earth-based intercepts demand $\Delta V$ on the order of $\sim$24 km s$^{-1}$ (with rapidly increasing values thereafter), while Mars-based intercepts could be achieved with $\Delta V$ as low as a few km s$^{-1}$, making them feasible with current capabilities. The study also discusses repurposing existing spacecraft around Mars and Earth-based observation platforms to observe 3I/ATLAS and to prepare for rapid responses to future interstellar objects, highlighting the importance of earlier detection for enabling lower-energy intercepts and impactful science. Overall, the work clarifies how mission feasibility and scientific return hinge on detection timing, orbital geometry, and rapid-use architectures for interstellar-object exploration.

Abstract

We investigate the feasibility of a spacecraft mission to conduct a flyby of 3I/ATLAS, the third macroscopic interstellar object discovered on July 1 2025, as it traverses the Solar System. There are both ready-to-launch spacecraft currently in storage on Earth, such as Janus, and spacecraft nearing the end of their missions at Mars. We calculate minimum $ΔV$ single-impulse direct transfer trajectories to 3I/ATLAS both from Earth and from Mars. We consider launch dates spanning January 2025 through March 2026 to explore obtainable and hypothetical mission scenarios. Post-discovery Earth departures require a challenging $ΔV\gtrsim24$ km s$^{-1}$ to fly by 3I/ATLAS. By contrast, Mars departures from July 2025 - September 2025 require $ΔV\sim5$ km s$^{-1}$ to achieve an early October flyby -- which is more feasible with existing propulsion capabilities. \added{We further calculate the phase angle and flyby velocity for these trajectories, noting that the resulting flyby speeds would impose significant observational and engineering challenges that a mission would need to overcome.} We discuss how existing spacecraft could be used to observe 3I/ATLAS and how spacecraft at other locations in the Solar System could be repurposed to visit future interstellar objects on short notice.

The Feasibility of a Spacecraft Flyby with the Third Interstellar Object 3I/ATLAS from Earth or Mars

TL;DR

This work addresses the feasibility of a spacecraft flyby of the interstellar object 3I/ATLAS using near-Earth or Mars-based assets. It develops a universal-variable Lambert-based framework to compute minimum-energy, direct-transfer trajectories, mapping the required , , flyby velocity, and phase angle across launch windows and documenting how discovery timing constrains practicality. The key finding is that post-discovery Earth-based intercepts demand on the order of 24 km s (with rapidly increasing values thereafter), while Mars-based intercepts could be achieved with as low as a few km s, making them feasible with current capabilities. The study also discusses repurposing existing spacecraft around Mars and Earth-based observation platforms to observe 3I/ATLAS and to prepare for rapid responses to future interstellar objects, highlighting the importance of earlier detection for enabling lower-energy intercepts and impactful science. Overall, the work clarifies how mission feasibility and scientific return hinge on detection timing, orbital geometry, and rapid-use architectures for interstellar-object exploration.

Abstract

We investigate the feasibility of a spacecraft mission to conduct a flyby of 3I/ATLAS, the third macroscopic interstellar object discovered on July 1 2025, as it traverses the Solar System. There are both ready-to-launch spacecraft currently in storage on Earth, such as Janus, and spacecraft nearing the end of their missions at Mars. We calculate minimum single-impulse direct transfer trajectories to 3I/ATLAS both from Earth and from Mars. We consider launch dates spanning January 2025 through March 2026 to explore obtainable and hypothetical mission scenarios. Post-discovery Earth departures require a challenging km s to fly by 3I/ATLAS. By contrast, Mars departures from July 2025 - September 2025 require km s to achieve an early October flyby -- which is more feasible with existing propulsion capabilities. \added{We further calculate the phase angle and flyby velocity for these trajectories, noting that the resulting flyby speeds would impose significant observational and engineering challenges that a mission would need to overcome.} We discuss how existing spacecraft could be used to observe 3I/ATLAS and how spacecraft at other locations in the Solar System could be repurposed to visit future interstellar objects on short notice.

Paper Structure

This paper contains 6 sections, 10 equations, 7 figures, 1 table.

Table of Contents

  1. Introduction
  2. Identification of Optimal Trajectories
  3. Optimal Trajectories from Earth
  4. Optimal Trajectories from Mars
  5. Discussion
  6. acknowledgments

Figures (7)

  • Figure 1: Direct flight $\Delta V$ values as a function of launch date for trajectories to 3I/ATLAS from Earth. The color of each point corresponds to the flight time of the mission. The upper- and lower-panels show direct flight $\Delta V$ values from 2025 January 1 -- 2026 March 31 and May 1 -- November 2 2025, respectively. The minimum post-discovery $\Delta V$ trajectory is 24.0 km s$^{-1}$(C$_3$ = 576 km$^{2}$ s$^{-2}$) on 2025 July 1 with a flight time of 137 days. Pre-discovery trajectories may have been feasible, requiring $\Delta V\sim7$ km s$^{-1}$ with a flight times of $\sim$250 days. The shaded region on the upper panel is the region shown in the lower panel.
  • Figure 2: Mission Design Contour displaying required $\Delta V$ (0--100 km $s^{-1}$) across Earth departure and 3I/ATLAS arrival dates. The Green circle mark indicates the minimum $\Delta V$ on discovery date, 2025 July 1.
  • Figure 3: The orbit of a post-discovery minimum $\Delta V$ mission to 3I/ATLAS sent on 2025 July 1 from the Earth. The spacecraft would encounter 3I/ATLAS on 2025 November 15 and would require $\Delta V= 24$ km s$^{-1}$. The trajectory for 3I/ATLAS, Earth, and the spacecraft are plotted in purple, blue, and gray, respectively. Markers represent departure location and flyby location, and arrows show direction of each orbit/trajectory. Points on each trajectory indicate the positions of each object every 30 days.
  • Figure 4: Similar to Figure \ref{['fig:earthmission_deltav']}, but for trajectories to 3I/ATLAS from Mars. Here, the shaded inset region is from 2025 July 1 to 2025 September 25. The minimum energy trajectory for a post-discovery mission would be launched on 2025 July 1 with a flight time of 94 days and require $\Delta V=$ 3.54 km s$^{-1}$. Pre-discovery trajectories would have required $\Delta V\sim3$ km s$^{-1}$(C$_3$ = 12.5 km$^{2}$ s$^{-2}$) with flight times of more than 200 days.
  • Figure 5: Similar to Figure \ref{['fig:earthmission_map']}, but from Mars in this case.
  • ...and 2 more figures