The Week in Space and Physics #4
Mars, all the evidence suggests, was once a habitable world. Oceans of liquid water may once have flooded the northern hemisphere, fed by networks of rivers and lakes stretching across the planet. The signs of this long-gone water are clear to see – but whether any life existed there, and how long that water survived, remains mysterious.
Two hints emerged this week that Mars may have been more habitable than thought. The first comes from an examination of Martian meteorites – chunks of Mars that have, over aeons, found their way to Earth. One such rock, found in the Sahara Desert a decade ago, has long been known to be ancient: perhaps as much as four billion years old.
A new analysis of this rock by Australian researchers revealed signs of shocked zircon. That, they say, can only be produced by large meteorite impacts: those as big as the one that wiped out the dinosaurs. Based on the age of the samples they tested, the researchers believe they were created by an impact 4.45 billion years ago.
Large impacts like this have dramatic effects on life. Should enough happen at once – as they probably did in the early Solar System – a planet can be effectively sterilised; wiped clean of life as oceans boil and fierce winds rip across continents. The evidence of this impact, then, implies Mars was not habitable 4.45 billion years ago.
It might, however, have been habitable after. Based on the evidence from this rock and other known big impacts, the researchers suggest conditions on Mars were comfortable for roughly four hundred million years. That period, they estimate, started around four billion years ago.
The second hint comes from a sample taken by the Curiosity rover on Mars. Analysis of that sample picked up an intriguing - almost curious - signal, one often associated with life back on Earth. Biologists have long known that living creatures favour a type of carbon known as C-12 over the heavier C-13. When scientists find samples with far more C-12 than should be present, then, they know they are probably looking at something biological.
That is exactly what Curiosity detected on Mars. Could the sample have been created by long ago Martians? It is possible; but, unfortunately, not the only explanation. Certain geological and atmospheric processes could have skewed the sample – or even, the researchers say, it could have come from an interstellar cloud passing through the Solar System. The question of whether life ever existed on Mars is still very much open.
The ISS Gets Another Decade in Space
After almost twenty-five years in orbit, the International Space Station is starting to show its age. Vital components are running years beyond their planned lifespan; some now require constant repair to avoid breakdown. Cracks, too, are appearing in the space station walls, creating slow air leaks and raising fears of sudden failure.
Even so, NASA is determined to keep the station running for another decade. In a recent report the agency outlined ambitious plans for the years ahead, a strategy to promote new commercial stations and a concept for how the station will, eventually, be de-orbited.
That decade will see the station complete a series of technology demonstrations: from proving the ominous sounding “faecal resource recovery” system to testing new space suits. The agency is also keen to expand commercial use of the station: a private company, Axiom Space, is expected to add several new modules over the next few years.
Those modules will provide new living space for astronauts, a lab facility and a viewing window. Axiom also plan to send their own astronauts to the station - with the first mission scheduled for March. Other space tourists are likely to follow - especially from Russia and other commercial partners.
That highlights NASA’s plan to replace the station. Instead of investing in an expensive new facility, the agency plans to promote commercial stations. Money has already been offered to several companies to help them come up with design. NASA hope at least one of these commercial stations will be in place by 2030, allowing the agency to simply purchase berths for its own astronauts.
Of course, those berths need not be limited to governmental astronauts. Once a commercial space station is in place, entry could be offered to whoever has the money to pay. That could include researchers and engineers - but it will also encourage tourism and allow the super rich to spend more time in space.
It is certainly possible, too, that the International Space Station survives beyond 2030. Original plans spoke of a fifteen year lifespan; one already exceeded by a decade. NASA may, if the condition of the station allows, decide to extend its mission by another five years or so – especially if commercial stations have not progressed as far as hoped.
If not, then the station will be de-orbited. Controllers will allow it to fall gradually back to Earth, until – a few hundred miles high – it starts to encounter the atmosphere. This, as the report states, is a point of no return. The station will start to burn, its structure stripped by hypersonic winds and soaring temperatures. Whatever survives that brief inferno will – if NASA line things up correctly – plunge into the Pacific Ocean; the final resting place for a wonder of human ingenuity.
Rogue Black Hole Spotted
How do you see a black hole? They are, as the name suggests, black, invisible against the darkness of the void. They give out no light, no radiation of any kind that can be seen by a telescope. True, some – like those at the hearts of galaxies – are surrounded by glowing clouds of dust, but many drift alone, hidden in the vastness of space.
Those rogue, isolated black holes do, however, have one telltale signature. As Einstein predicted a century ago, massive and dense objects like black holes warp space slightly. Should a black hole pass between Earth and a star, then, the light from that star will appear to dance and brighten; a motion caused by the passage of light through that warped space.
This effect is small and hard to detect. Back in 2011, however, two teams of astronomers spotted a star suddenly brighten and fade. Over the next six years astronomers monitored the star, finding that the position of the star had also changed – a clear sign of the warping effect. Precise measurements suggested the presence of a black hole, one seven times heavier than the Sun.
Such discoveries are rare at the moment. Few rogue black holes have ever been found, and none has ever been probed in as much detail as this one. But astronomers are busy mapping the sky in ever more detail. New telescopes – including the Vera Rubin observatory in Chile and the upcoming Nancy Grace Roman telescope – should reveal hundreds more.
New Planets around Old Stars
Our solar system formed when the Sun was young; likely when it was a few tens of millions of years old. Astronomers have long thought that all planets formed in a similar way: slowly condensing from the rubble and debris around a young star. Yet new evidence suggests some planets could form much later, taking life from the death of an old star.
Many stars exist in pairs: so-called binary stars. Those pairs do not always age at the same rate – and indeed, one of the two stars may begin to die millions of years before the other. As it does, the surviving star may begin to strip gas and dust from the dying star; thus forming a ring of debris around itself.
A recent examination of dozens of these rings revealed the presence of gaps. Those, astronomers think, are caused by new born planets. New worlds, in other words, seem to be forming from the ashes of dying stars.