The fly-by technique is a very common one for spacecraft, as they depart from the Earth to other destinations inside the solar system, or beyond. In order to limit the amount of fuel these probes carry, they are set on trajectories that bring them very close to a planet or other celestial body, but without being captured by that body's gravitational pull. This considerably increases their speed, without the need for very advanced motors or large fuel sources. However, as spacecraft have flown by the Earth, astronomers have detected a peculiarity that they cannot explain yet.

As the probes have flown past our planet, ground-based monitoring networks have picked up step-like changes in velocity, rather than a smooth, constant increase. This has had astronomers scratching their heads for a while, as no clear answer seems to be presenting itself. Last year, Princeton University expert Stephen Adler proposed that the phenomenon might be occurring as probes started slamming into particles of dark matter, as they neared the point of closest approach to the Earth.

Adler even calculated the hypothetical distribution of these particles, based on measurements collected from the speeds of several spacecraft using the Earth for a fly-by. He determined that a halo of them had to exist around the planet, and offered a theoretical model to explain their spread. The expert also determined that two kinds of dark-matter particles must exist, as some spacecraft seemed to accelerate, while others decelerated on approach.

Now, the expert returns with a further explanation of the peculiar phenomenon. He says that, as two bodies collide, some of the kinetic energy is transformed into heat, and that there is no reason to believe that interactions between normal and dark matter do not respect this rule. As such, he suggests, experts should be looking at the temperatures each of the spacecraft in the study have had when they have approached the planet. He also believes that mining historical records of craft passing by should yield clues as to whether some of them heated unexpectedly.

If that turns out to be the case, then dark matter does not only exist hypothetically, but it's also located in a halo around our planet, slamming into our space probes. That could open up the way to a new kind of physics, the expert concludes. Critics to his model believe that the anomalies are simply the result of errors from current orbital data-fitting techniques, Technology Review reports.