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Where did all the Martian water go?
NEWS & TECHNOLOGY
Lisa Grossman
MARS has a real water shortage. It seems we have either misunderstood what its early years were like – or vast amounts of water are hiding beneath its surface. A lot of evidence points towards Mars being warm and wet early in its history; features that look like rivers, lakes and outflows have been spotted both from orbit and by rovers on the
Orcas seen hunting rare beaked whales ORCAS off the coast of Australia have been seen killing and eating rare beaked whales – a behaviour never observed before. Since 2014, a small team including Rebecca Wellard at Curtin University in Perth have joined commercial whale-watching trips to study orcas, or killer whales, off Australia’s south coast. On four occasions, they 12 | NewScientist | 7 January 2017
photographed groups of up to 20 orcas attacking lone beaked whales. Those whales were similar in size to the orcas hunting them. The hunts lasted an hour or two. The orcas chased the whales and eventually killed them by biting them and forcing them underwater to drown them. On two occasions they were seen stripping carcasses of skin, suggesting these are predatory attacks (PLoS One, doi.org/bvzt). Little is known about the orcas that live around Australia. But it is known that populations elsewhere in the world have their own distinct cultures
REBECCA WELLARD
NASA/JPL/UNIVERSITY OF ARIZONA
Where did all the Martian water go?
atmosphere to build up an climate through time.” inventory of everything that The trouble is, that’s less water enters and leaves over time. It than expected. In 2015, James Head also estimates the total loss by at Brown University and Michael measuring the fraction of heavier Carr at the US Geological Survey isotopes of certain atoms versus estimated that the equivalent of a their lighter counterparts. As the global ocean a few hundred metres lighter versions are easier to deep was needed to explain all the knock out into space with a stray geological features that look like cosmic ray or extra energy from they were formed by water. solar photons, a higher fraction “We were counting on their loss of heavy isotopes remaining in rate to explain it,” Head says. Mars’s present-day atmosphere “And they didn’t come through.” means much of the original One possible reason for the atmosphere has been lost. discrepancy is that the long-held MAVEN focuses on hydrogen and oxygen as ways to trace water “Loss of gas to space is likely a major process for and carbon dioxide, and neutral changing the Mars climate argon as a way to measure the sheer volume of atmosphere loss. through time” Based on measurements of these taken over a full Martian year, notion of Mars being like Earth in the team concludes that about the past is wrong. One theory has 4 billion years ago, the Red Planet’s it that the planet was actually cold atmospheric pressure – currently and dry, and that streams and –Formed by water?– less than 1 per cent of Earth’s – rivers formed underneath the ice was up to 1.5 times what Earth’s pack instead of via water flowing surface, and a lot of the planet’s is today. They also found that it on the surface. All that would be minerals contain water. could have had the equivalent needed is a slightly denser CO2 atmosphere – which MAVEN’s So where did all this water of a global ocean between 2 and go? The Mars Atmosphere and 40 metres deep in its distant past. measurements suggest you had. The other option is that the Volatile Evolution (MAVEN) “It’s a consistent story,” said water is hidden away somewhere, spacecraft was sent to find the team leader Bruce Jakosky at the maybe underground. Dark streaks answer. Since its arrival at Mars in Laboratory for Atmospheric and 2014, it has been measuring how Space Physics in Boulder, Colorado, recently spotted on crater rims much atmosphere Mars is losing who presented the findings at the that look like they could be liquid water may be fed by underground to space. From that, we can figure American Geophysical Union aquifers, for instance. out how much it had in the past. meeting in San Francisco in “Either it’s hidden somewhere, The orbiter keeps track of both December. “Loss of gas to space or there wasn’t that much to start the activity of the sun and the ions is likely a major if not the major with,” says Carr. n streaming away from the planet’s process for changing the Mars
and specialise in particular prey. Some feed on fish such as herring, while others hunt mammals such as seals, dolphins and the calves of large whales. The 2001 BBC documentary The Blue Planet famously featured footage of orcas pursuing and killing a grey whale calf despite the mother’s efforts to protect it. Little is known about beaked whales. They are rare, hard to spot on the surface and feed in deep waters. The species preyed on in Australia is thought to be young or female strap-toothed whales (Mesoplodon –Killer whales are whale killers– layardii). Michael Le Page n
Lisa Grossman
MARS has a real water shortage. It seems we have either misunderstood what its early years were like – or vast amounts of water are hiding beneath its surface. A lot of evidence points towards Mars being warm and wet early in its history; features that look like rivers, lakes and outflows have been spotted both from orbit and by rovers on the
Orcas seen hunting rare beaked whales ORCAS off the coast of Australia have been seen killing and eating rare beaked whales – a behaviour never observed before. Since 2014, a small team including Rebecca Wellard at Curtin University in Perth have joined commercial whale-watching trips to study orcas, or killer whales, off Australia’s south coast. On four occasions, they 12 | NewScientist | 7 January 2017
photographed groups of up to 20 orcas attacking lone beaked whales. Those whales were similar in size to the orcas hunting them. The hunts lasted an hour or two. The orcas chased the whales and eventually killed them by biting them and forcing them underwater to drown them. On two occasions they were seen stripping carcasses of skin, suggesting these are predatory attacks (PLoS One, doi.org/bvzt). Little is known about the orcas that live around Australia. But it is known that populations elsewhere in the world have their own distinct cultures
REBECCA WELLARD
NASA/JPL/UNIVERSITY OF ARIZONA
Where did all the Martian water go?
atmosphere to build up an climate through time.” inventory of everything that The trouble is, that’s less water enters and leaves over time. It than expected. In 2015, James Head also estimates the total loss by at Brown University and Michael measuring the fraction of heavier Carr at the US Geological Survey isotopes of certain atoms versus estimated that the equivalent of a their lighter counterparts. As the global ocean a few hundred metres lighter versions are easier to deep was needed to explain all the knock out into space with a stray geological features that look like cosmic ray or extra energy from they were formed by water. solar photons, a higher fraction “We were counting on their loss of heavy isotopes remaining in rate to explain it,” Head says. Mars’s present-day atmosphere “And they didn’t come through.” means much of the original One possible reason for the atmosphere has been lost. discrepancy is that the long-held MAVEN focuses on hydrogen and oxygen as ways to trace water “Loss of gas to space is likely a major process for and carbon dioxide, and neutral changing the Mars climate argon as a way to measure the sheer volume of atmosphere loss. through time” Based on measurements of these taken over a full Martian year, notion of Mars being like Earth in the team concludes that about the past is wrong. One theory has 4 billion years ago, the Red Planet’s it that the planet was actually cold atmospheric pressure – currently and dry, and that streams and –Formed by water?– less than 1 per cent of Earth’s – rivers formed underneath the ice was up to 1.5 times what Earth’s pack instead of via water flowing surface, and a lot of the planet’s is today. They also found that it on the surface. All that would be minerals contain water. could have had the equivalent needed is a slightly denser CO2 atmosphere – which MAVEN’s So where did all this water of a global ocean between 2 and go? The Mars Atmosphere and 40 metres deep in its distant past. measurements suggest you had. The other option is that the Volatile Evolution (MAVEN) “It’s a consistent story,” said water is hidden away somewhere, spacecraft was sent to find the team leader Bruce Jakosky at the maybe underground. Dark streaks answer. Since its arrival at Mars in Laboratory for Atmospheric and 2014, it has been measuring how Space Physics in Boulder, Colorado, recently spotted on crater rims much atmosphere Mars is losing who presented the findings at the that look like they could be liquid water may be fed by underground to space. From that, we can figure American Geophysical Union aquifers, for instance. out how much it had in the past. meeting in San Francisco in “Either it’s hidden somewhere, The orbiter keeps track of both December. “Loss of gas to space or there wasn’t that much to start the activity of the sun and the ions is likely a major if not the major with,” says Carr. n streaming away from the planet’s process for changing the Mars
and specialise in particular prey. Some feed on fish such as herring, while others hunt mammals such as seals, dolphins and the calves of large whales. The 2001 BBC documentary The Blue Planet famously featured footage of orcas pursuing and killing a grey whale calf despite the mother’s efforts to protect it. Little is known about beaked whales. They are rare, hard to spot on the surface and feed in deep waters. The species preyed on in Australia is thought to be young or female strap-toothed whales (Mesoplodon –Killer whales are whale killers– layardii). Michael Le Page n