In a groundbreaking study, physicists at the Massachusetts Institute of Technology (MIT) have suggested that monitoring the wobble of Mars’ orbit over time could serve as a novel method to detect the elusive dark matter. This research, published on September 17 in the journal Physical Review D, posits that primordial black holes, which may constitute a significant portion of the universe’s dark matter, could be detected through their gravitational influence on the orbit of Mars.
An artist’s illustration depicts a primordial black hole (left) flying past and causing a brief wobble in Mars’ orbit (right), with the Sun in the background. Scientists at MIT say that this wobble can be detected by current instruments. Image credit: Benjamin Lehmann using SpaceEngine @ Cosmographic Software LLC.
The concept of dark matter has long perplexed scientists, as it constitutes approximately 80% of the universe’s total mass. invisible to electromagnetic radiation but detectable through its gravitational effects on visible matter. The prevailing theory suggests that dark matter is composed of exotic particles, but despite extensive searches, no such particles have been found.
Primordial Black Holes as Dark Matter Candidates
The idea that dark matter might be composed of primordial black holes, formed in the early moments after the Big Bang, was first proposed in the 1970s. Unlike astrophysical black holes formed by the collapse of massive stars, primordial black holes result from the collapse of dense regions in the early universe. These black holes could range in size from that of an atom to the largest of asteroids, and their gravitational influence might account for some of the dark matter.
David Kaiser, a physics professor at MIT and a Germeshausen Professor of the History of Science, explains, After decades of precise ranging, scientists’ understanding of the distance between Earth and Mars is accurate to about 10 centimeters. We are leveraging this highly instrumented space environment to look for tiny effects. If we see something, it would give us reason to pursue this delightful idea that all dark matter is composed of black holes that formed less than a second after the Big Bang and have been flowing through the universe for 14 billion years.
The Mars Wobble Detection Method
The research team, led by Kaiser, simulated the dynamics of the solar system to understand the potential effects of a primordial black hole passing through. They calculated the speed of such black holes based on the estimated amount of dark matter in a specific space region and their assumed mass, comparable to the largest asteroid in the solar system.
The team focused on the effects of these black holes on the planets, particularly Mars. They found that if a primordial black hole passed within a few billion miles of Mars, it would cause a slight wobble or shift in the planet’s orbit. This wobble would amount to about one meter over the course of several years—a minuscule change considering Mars is over 140 million miles from Earth. However, current high-precision instruments monitoring Mars could detect this subtle shift.
Challenges and Future Research
The researchers acknowledge that even if such a wobble is detected in the coming decades, there would still be significant work to do to confirm that the disturbance was caused by a passing black hole rather than a mundane asteroid. To achieve this, they are collaborating with experts who have rich experience in simulating the dynamics of more celestial bodies in the solar system.
Sarah Geller, a co-author of the study and a postdoctoral fellow at the University of California, Santa Cruz, says, We are now working to simulate a large number of celestial bodies, from planets to satellites and asteroids, and how they move over long time scales. We hope to inject close encounter scenarios and study their effects with higher precision.
While the research presents a promising new approach to detecting dark matter, it also acknowledges the element of luck involved. Matt Caplan, an assistant professor of physics at Illinois State University, notes, This is a very clever test they’ve proposed that could tell us if nearby black holes are closer than we think. I want to emphasize that there’s also a bit of luck involved. Whether the search finds a loud and clear signal depends on the exact path that the wandering black hole takes through the solar system. Now that they’ve validated the idea with simulations, they must do the hardest part—examining real data.
The study opens up new avenues for understanding dark matter and its origins, offering a fresh perspective on a mystery that has long intrigued scientists.
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