Three stories today. In one crater on Mars, water has been read as having wetted the rock at least three times, in three different ways; a signal long taken as evidence that the whole Earth was overturned two billion years ago may have been the affair of a single region. And on entering dreaming sleep, more blood goes to the brain, yet the energy of the nerve cells was falling.
Space
The Perseverance rover swept the rocks of Jezero crater with a laser and picked out the traces of water passing three times, in three different ways.
Jezero crater on Mars is thought to have been a lake long ago. The Perseverance rover examined the rocks at the edge of that lake. The rover carries an instrument that fires a laser at a distant rock to make it very hot, then splits the colours of the light that comes off to read what it is made of. More than a hundred and eighty-five spots on the rocks were read this way.
The picture that emerged was not of water once. First, groundwater with carbon dioxide dissolved in it seeped into cracks in the rock and left carbonate. Next, lake water reached it and left silica. Last, heated groundwater flowed through and made veins of mineral about as thick as two finger joints. When water like this meets a mineral called olivine, hydrogen is produced. Hydrogen is food for some microbes. And carbonate and silica are rocks that hold on to traces of life for a long time.
Through the eyes of the AtlasThe Library piece “Every Beam Carries the Star's Name Tag” is about the method of splitting light to read what something is made of. That method is not used on stars alone. On the ground of Mars too, the name of a rock is read from one laser shot and the colours of its light. As with the story of the Martian gullies here on 12 September, the question of water on Mars has moved from whether there was any to when, and what kind of water it was.
A word of cautionNo trace of life has been found. A closer look will have to wait until the samples the rover has stored are brought back to Earth.
Source · ScienceDaily (NASA Jet Propulsion Laboratory · Purdue University)
Earth
A fresh analysis of the carbon signal in two-billion-year-old Russian rock layers suggests it may be not a change across the whole Earth but a trace made in a single basin by magma and microbes.
Carbon has siblings that differ slightly in weight. Their proportions shift as living things live and die, so the carbon ratio in old rock is read as a record of how the Earth was getting along at the time. An unusual carbon signal from the Zaonega rock layers in Russia, two billion years old, was long taken as evidence that the carbon cycle of the whole Earth had been badly shaken. It mattered all the more because it coincided with the time oxygen began to build up in the air.
Researchers at Caltech in the United States looked into the very small droplets and gases trapped in that rock. Tracing back the temperatures the rock had been through, they found a steep difference: close to 350 degrees at the bottom and lower further up. That is the mark of a place where a sheet of magma pushed into sediments under the sea. With that heat, gases such as methane could have formed from the organic matter in the sediments, and the bodies left by microbes that fed on them could have made the signal seen today. In other words, the affair not of the whole Earth but of one basin.
Through the eyes of the AtlasThe Library piece on microbes and the Earth's oxygen is the story that the air we breathe now was made by microbes. One piece of the evidence propping up that large story was shaken today. In science this kind of re-reading is common; the story does not collapse, but the extent of what is certain is narrowed down.
A word of cautionThe possibility that other processes were mixed in has not been ruled out. Rocks from Gabon in Africa that show the same signal have still to be checked.
Source · ScienceDaily (Caltech)
Life
From about fifty seconds before REM sleep begins, the blood going to the brain increases, yet the energy-carrying substance inside the nerve cells actually falls.
When the brain works hard, that much more blood arrives. Blood brings oxygen and sugar, so it seems only natural that as much comes as is used.
Researchers at Tohoku University in Japan made the skulls of mice transparent and looked straight at the surface of the brain as the animals slept. They measured, all at once, the amount of blood, the energy-carrying substance in the nerve cells, and the fuel of the cells that support the nerves. From about fifty seconds before REM sleep began, the blood started to increase, and it went on increasing through REM sleep. But in that time the energy-carrying substance in the nerve cells fell. More fuel was arriving while the storehouse was emptying. The researchers think that during REM sleep the nerve cells are using energy faster than the fuel can arrive. That fits the conjecture that it is a busy time of sorting memories.
Through the eyes of the AtlasThe Library piece “The Brain Runs on Twenty Watts” is about why the brain runs on as much electricity as a single light bulb. Today's story shows where, at different times, the brain directs that small supply of energy. On 27 September there was a story here that people with longer REM sleep had fewer illnesses; today, one more layer of what goes on inside the brain during that sleep has come to light.
A word of cautionThis is a result seen in mice. Why the energy falls, and what it is being used for, is not yet known.
Source · ScienceDaily (Tohoku University)