Reports of Pioneer 10's death, it turns out, have been greatly exaggerated. The last signal picked up from the probe, now heading out of the solar system, was in August 2000. Several attempts to reestablish contact with the spacecraft since then had been unsuccessful and ground controllers feared the worst. However, on Saturday April 28, faint telemetry from Pioneer 10 was picked up at the Deep Space Network station in Madrid in response to an uplink signal sent out to the probe. Pioneer 10 is currently 7.29 billion miles from Earth – almost 11 hours away at light-speed – and is heading out from the sun at 27,380 miles per hour.
Planets in Orion? The controversy grows
(Apr. 27, 2001)
A team of astronomers, led by Henry Throop at the Southwestern Research Institute, claims it has found dust grains in the process of growing into protoplanets within the Orion Nebula. Moreover, the planets being formed, it says, are more likely to end up small and rocky, like the Earth, than large and gassy, like Jupiter. Large stellar nurseries, like Orion, bathed in intense ultraviolet radiation from hot, newborn stars, pose problems for would-be planets. The UV will tend to destroy any nascent disks of dust and gas from which planetary systems can form. But Throop and his team have found evidence of large grains in Orion which they believe could be in the process of sticking together to make planetesimals and planets – but only small ones. Jupiter-sized worlds take upwards of a million years to accumulate, which is at least ten times longer than a dust disk could survive in such a radiation battered environment. Others, notably JPL's Karl Stapelfeldt, challenge the notion that even terrestrial-sized worlds would have time to grow. Both Throop's team and Stapelfeldt present their views in this week's issue of the Science. For more, go here.
Meanwhile, controversy still surrounds the discovery, announced last year, of free-floating gas giants in the Orion Nebula. Are these truly planets or larger objects such as brown dwarfs? For more on this, go here.
New Scout-class probe for Mars reconnaissance
(Apr. 21, 2001)
NASA is investing about $300 million this year to develop designs for a new class of Mars explorer known as Mars Scouts. These probes – the first of which could be launched as soon as 2006 – could take a variety of forms include balloons, aerobots, gliders, and penetrators, as well as the more familiar landers and rovers. One of their tasks will be to follow up interesting discoveries made by the core missions already planned over the coming decade.
Mars and Moon meteorite finds
(Apr. 16, 2001)
Two meteorites believed to have originated on Mars and the Moon have been discovered in northwest Africa. They bring to 17 and 15, respectively, the number of rocks on Earth thought to have come from these worlds. Details of the discoveries will be reported in the July bulletin of the Meteoritical Society.
The earliest seafloor hydrothermal vents – supposedly more than three billion years old – may be nothing more than deposits from underground springs active in the last few thousand years. That is the claim of two US geologists who carried out a new analysis of rocks from South Africa which were previously dated to the Archaean period – when life first began to diversify. The findings could have important implications for our understanding of the early Earth and the microbial life forms that lived there. But one authority on the geology of the Barberton greenstone belt – where the rocks are found – launched a vigorous defence of evidence that they contain ancient hydrothermal vents.
NASA's latest probe to Mars was launched successfully toward the Red Planet yesterday. From orbit, 2001 Mars Odyssey will investigate the planet with instruments designed to tell us more about the surface mineralogy and on-orbit radiation environment. Of great relevance to the quest for Martian life will be Odyssey's ability to detect traces of water just below the surface, if any exists. If all goes well, the probe will reach its destination on October 24.
Eleven more planets have been found around Sun-like stars, including one in an Earth-like orbit. The announcement came from astronomers working at ESO's La Silla observatory. Another of the new worlds is in a trinary system so that its sky will be illuminated by three suns. In a separate announcement, a British team says that it has found 13 more "free-floating" planets in the Orion Nebula.
For more, go here (BBC) and here (Spaceflight Now).
ALH 84001: Does it really contain life signs?
(Apr. 2, 2001)
Since the dramatic 1996 announcement by a team of scientists from NASA's Johnson Space Center and Stanford, intense debate has centered on the purported biogenic traces in the Martian meteorite ALH 84001 (and, more recently, a couple of other stones known to have come from the fourth planet). What is the consensus today? The fact is, there still isn't one. But the debate has become more focussed and now involves principally the origin of the tiny embedded magnetite crystals. If these crystals had been found in a terrestrial sample, they may already have been accepted as traces of ancient bacteria. Afterall, we expect to find life or the remains of it virtually everywhere we look on this planet. Intriguingly, the characteristics of the Martian magnetite are exactly the same as those of magnetite produced by Earthly bacteria and no one has shown how this precise combination of characteristics could have been produced by a purely chemically process. However, a huge issue is at stake: scientists are trying to decide if they're prepared to accept definitively that we have found the first example of life beyond the Earth. As the adage goes: "Extraordinary claims require extraordinary evidence." Critics of the biogenic thesis argue that just because we don't know of a way to generate these chains of magnetite crystal abiotically doesn't mean that there isn't one. It's becoming clear that the scientific community is not likely to jump up one day and collectively shout "Eureka, we've found alien life!" Rather, the case for organisms elsewhere will have to be compiled slowly and carefully, perhaps over several more years. This cautious, meticulous approach is a sure indication that astrobiology is maturing as a science.
For more on the issues involved, go here (Astrobiology Institute) and here (space.com).
