MMX on Phobos: Japan's Martian Moon Sample Return and the Redefinition of Time

Episode snapshot

The podcast surveys two frontier themes: a space mission to Phobos as part of Japan and JAXA's Martian Moons Exploration MMX program, and the rethinking of time itself as leap seconds are phased out. A Martian moon sampling plan, the autonomously operated Edifix rover, and the challenges of low gravity are explored alongside a major metrology shift that redefines the second using advanced clocks and relativistic corrections. The episode also touches on AI in mathematics, and a climate-history case study, all tying into how science pushes the boundaries of what we can measure, build and understand.

• MMX Phobos mission details including Edifix rover, autonomous sampling, and sample return
• Leap seconds abolition and time definition based on optical clocks and relativity
• Mathematics and AI: the Association of Human Mathematics and questions of human versus machine creativity
• Barnes Ice Cap and the start of a potential next ice age in the context of modern warming

Overview

In this episode the Inside Science team returns with a focus on two big topics that sit at the intersection of space science and fundamental physics. The first is a mission to Mars two small moons, specifically Phobos, which is the target of Japan’s Martian Moons Exploration MMX program. The second is a rethink of how we define time, prompted by the decision of the International Bureau of Weights and Measures to abolish leap seconds and to redefine the second using increasingly precise atomic clocks. The discussion threads weave through robotics in extreme environments, the physics of time, the role of AI in mathematics, and a climate history case that questions long held assumptions about ice ages. The podcast uses expert interviews to illuminate not just what is being studied, but how researchers approach the limits of measurement, computation and prediction.

MMX and Phobos: sampling a Martian moon

The MMX mission is a Japanese-led effort to study and return samples from Phobos, one of Mars’s moons. The main spacecraft will remain in orbit around Phobos for several months gathering data with multiple instruments, while a small rover, Edifix, will explore the moon’s surface. Phobos has extremely weak gravity, roughly 1,500 to 2,000 times weaker than Earth’s, which creates unique challenges for movement and sampling. The rover must operate autonomously to navigate the surface, manage its power, and deploy sampling mechanisms while staying in communications range of the MMX orbiter. Where and how Edifix will observe the landing or observe sampling operations is still under discussion, as is how close it will be to the main MMX spacecraft when the sample collection occurs. The plan is to leave Edifix on Phobos to collect a set of surface samples and then lift off, letting the MMX spacecraft move away and return to Earth with the cargo. The Japanese heritage of sample return missions, drawing on Hayabusa and Hayabusa 2, informs the MMX design and approach. The interview also delves into the difficulties of driving on Phobos’s surface where traction comes from gravity, so rover speed must be extremely limited, and the rover will need to be highly autonomous to upright itself and manage its solar panels after landing.

Time and the leap second reform

Time is a central theme in metrology and physics, and this episode explains why the leap second is being abolished. Since 1972, leap seconds have been added to keep civil time aligned with Earth’s rotation. With advances in atomic timekeeping, there is growing support for letting clocks drift for long spans of time and then making corrections when the discrepancy becomes significant. The interview with a Time Standards expert at the National Physical Laboratory in the UK explains how the current second is defined by a cesium atom, and how optical atomic clocks—hundreds of times more precise—will enable more accurate realizations of time. Relativity plays a role because clocks at different gravitational potentials run at different rates, so even altitude and solid Earth tides induced by the Moon must be accounted for when comparing clocks. A target date of 2030 is set for a redefinition of the second, a move that will require careful calibration and widespread adoption to avoid any perceived disruption.

AI, mathematics and the human touch

The program also covers how AI is transforming mathematics. A global development has seen more than a thousand mathematicians join the Association of Human Mathematics, which endorses pledges that range from avoiding AI-assisted writing to embracing limited, ethical AI usage. Speakers reflect on whether mathematics is inherently a human creative act or something that machines might eventually supersede. The discussion touches on the security implications of AI in cryptography and how some researchers worry that new algorithms discovered by AI could undermine current cryptographic standards, potentially affecting Internet security. The segment frames this moment as a rethinking of what it means to do math when AI can assist, verify or even formalize proofs, and what human insight still contributes uniquely to the discipline.

Ice ages and climate context

In the climate science thread, the podcast revisits the Barnes Ice Cap on Baffin Island and its relation to the Laurentide Ice Sheet. New findings suggest that around Roman times the Laurentide was not shrinking but expanding; about 2,000 years ago it began to re-expand, which would have signaled the onset of the next ice age had human forcing not altered the trajectory. The current trajectory shows that, with greenhouse gas concentrations at present and projected into the near future, a new ice age is unlikely on human timescales, although natural glaciation cycles have varied widely over tens of thousands of years. The discussion places this in the broader context of how climate feedbacks, ocean and atmospheric dynamics, and human activity interact to influence long-term ice sheet behavior.

Closing notes

The episode closes with a rapid recap and a sense of the ongoing journey in exploring extreme environments, redefining time, and pushing the boundaries of what we can measure, model and understand in science.