The Week in Space and Physics: An Interstellar Meteor?
On claims of an interstellar meteor, a theory to replace dark matter, trouble with Voyager and a giant Martian volcano

The facts are these. At a little past three in the morning of January 9, 2014, something exploded over the western Pacific Ocean. The event was picked up by military sensors, which showed a fast moving object had struck the Earth and then detonated in the atmosphere. It was, in all probability, a small asteroid encountering our world.
This is not controversial. Such things happen all the time, and are regularly picked up by various sensors designed to look for atmospheric explosions. They cause little harm and, apart from the occasional flash in the sky, draw little attention.
Yet for Avi Loeb, a professor at Harvard University, the event was worth investigating in detail. Sensors showed the meteor hit the Earth at an unusually fast speed, which may indicate it had come from beyond the edge of the solar system. Classified - and therefore vague - information from the US military seems to support that assessment. If so, this is an exciting discovery. No other meteor has ever been tracked to such an interstellar origin.
Last year Loeb led an expedition to scour the seafloor for traces of the meteor. He claims to have found them: a magnetic sledge brought up hundreds of tiny metallic spheres from the seabed. Analysis of them showed a mix of elements that - according to Loeb at least - can only have come from beyond the solar system.
The rest of the astronomical community is not so sure. Proving the small spheres have an interstellar origin is all but impossible, they say. Even worse, the ocean floor is expected to be littered with debris of this kind - some of it from meteors, but much of it from less exotic sources.
In a recent paper Steve Desch, an astrophysicist at Arizona State University, disputed Leob’s assessment of the spheres. The mix of elements they contain, he says, is indeed found in our solar system, and even on the Earth itself. He identifies them as probable debris from a much earlier asteroid impact, one that struck Australia hundreds of thousands of years ago.
The composition of the spheres matches rocks found in northern Australia, Desch says, and come from a type of iron rich sandstone. After the asteroid hit, that sandstone was blasted upwards, and later fell across much of the Earth in the form of small molten balls. Similar debris from the impact, he points out, has been found across the Pacific and Indian oceans.
Loeb has argued back, saying that spheres from such a long ago impact should by now be buried deeply in the ocean floor. But Desch’s calculations suggest they’d probably only be a few centimetres deep, and so could have been pulled out by Loeb’s sledge.
Unfortunately for Loeb there is little in the way of solid evidence his meteor really came from beyond the solar system, or even that the spheres he has found came from space at all. We probably will encounter interstellar material one day, but this is not it.
The End for Dark Matter?
For decades observations of the cosmos have been troubling physicists. Galaxies spin too fast, they group together when they ought to fly apart, and they distort space more than they look like they should. Either our laws of gravity are wrong, or there is more matter out there than we can see.
Most physicists favour the second option. Trouble is, there has to be an awful lot of extra matter to make the sums add up. This dark matter should account for at least eighty percent of most galaxies, and that, given we have never found an ounce of the stuff on Earth, is rather troubling.
On the other hand, we do have good reason for thinking something might be up with gravity. Unlike the other forces of nature, which are all covered by quantum theory, gravity is described only by Einstein’s general relativity. Relativity and quantum theory view the universe in very different ways, and are generally regarded as incompatible with each other.
Most of the time this problem can be sidestepped. Quantum things tend to be small things, which means the force of gravity can be ignored. Big things, like galaxies, don’t behave in quantum ways. Only when we encounter small and heavy things like black holes do the theories collide and break down.
It is possible that a quantum theory of gravity might solve the problem of dark matter. But despite decades of work, we still don’t have a convincing theory that fits. Now, in a set of papers, a pair of physicists at University College London have proposed a ‘post-quantum’ theory of gravity that they say eliminates the need for dark matter.
Their theory does not attempt to describe gravity in a quantum way. Instead it keeps many of the features of Einstein’s relativity, while introducing an element of randomness into the way it works. That allows the mathematics to work together with quantum physics and thus produces a consistent theory covering both.
When they applied this new theory on a cosmic scale, they were able to predict the rotation of galaxies without needing to add any extra dark matter. They also found parameters that look rather like dark energy, perhaps eliminating the need for that mysterious force. Overall, then, this looks like a promising new approach.
It is not, however, yet a solution for the troublesome questions of dark matter and energy. Much more work and evidence will be needed for that. But it is, at least, some fresh thinking in a field that badly needs some good ideas.
A Voyager in Distress
With every passing day Voyager 1 traverses another million miles of space. It has, in its forty-six years of flight, covered more than fifteen billion miles, marking it out as the most distant human-made object from Earth.
Unfortunately Voyager 1 also seems to be in trouble. For the past few months the spacecraft has been unable to transmit data back to Earth, leaving its operators in the dark about its status. The issue seems to lie in a subsystem known as the flight data system, one of three onboard computers.
Normally this system packages data before it is transmitted back to Earth. For reasons unknown, however, it has stopped working properly. Instead of sending back data, Voyager is transmitting a steady radio tone. Although that confirms the spacecraft is still alive, it contains no other useful information.
After troubleshooting the problem for more than three months, NASA operators finally made some progress at the start of March. Thanks to a command sent then, the radio tone has since been replaced with a readout of the flight data system memory.
NASA is hoping that a careful analysis of this data will reveal the problem with Voyager 1. If so, operators may be able to devise a fix that will allow Voyager to once again send scientific and engineering data back to Earth from its distant viewpoint.
Still, whatever they do, Voyager’s days are numbered. After close to half a century in space its plutonium batteries are beginning to run low on power. Within the next decade operators will begin switching off its instruments and gradually start bringing its long mission to an end.
Mars’ Hidden Volcano
Buried in plain sight is a giant Martian volcano, according to a recent report. The volcano, which lies at one end of the vast Valles Marineris Canyon on Mars, is said to be higher than Mount Everest and more than four hundred kilometres wide.
Although the area has been studied before, researchers had previously missed the volcano. That is in part because the surface of the volcano is heavily eroded and scarred with deep canyons and valleys. From orbit it thus appears more as a fragmented maze than as a towering mountain.
The landscape around the volcano seems to have a complex and violent history. Repeated eruptions must have built the mountain up over millions of years. Yet signs of glaciers exist, and the interaction of ice and lava might have caused parts of the volcano to dramatically fracture and collapse. Certainly it will be an interesting target for any future explorers of Mars.
This was a fascinating set of articles and I'm happy to be a new subscriber! Restacking to Notes.
You say you lost your religion? GOOD. Sorry—not really—if that comment offends any of your readers. IMO, religion is entirely based upon acceptance of myth without supporting evidence. Once one loses their religion, one can start walking the path to see realty based upon one’s level of curiosity to learn and willingness to open one’s eyes. I have learned that there is very little that I was taught earlier in life that is true.