[ti:NASA Rover Captures Rock Showing Possible Signs of Microbial Life]
[by:www.21voa.com]
[00:00.00]更多听力请访问21VOA.COM
[00:00.04]A Mars explorer operated
[00:02.92]by the American space agency NASA
[00:06.36]has captured a rock that scientists say
[00:10.96]shows possible signs of ancient microbial life.
[00:15.92]NASA said in a recent statement
[00:19.60]that the Perseverance explorer, or rover,
[00:23.72]collected the rock on July 21.
[00:27.24]Scientists working on the Perseverance team
[00:31.72]nicknamed the rock "Cheyava Falls,"
[00:34.72]after the tallest waterfall in the Grand Canyon.
[00:39.20]The rover's exploration area is believed
[00:43.32]to include a former river valley
[00:46.48]measuring about 400 meters wide.
[00:49.80]The valley is thought to have formed by water
[00:54.16]rushing into Jezero Crater billions of years ago.
[01:00.12]Scientists believe the area around Jezero Crater
[01:05.08]contained large bodies of water in the distant past.
[01:09.96]NASA's statement says the rock shows signs of
[01:15.12]"chemical signatures and structures
[01:18.28]that could possibly have been formed
[01:21.16]by life billions of years ago..."
[01:24.64]NASA team members based their findings
[01:28.48]on examinations of the rock with imaging equipment
[01:32.48]and multiple scientific instruments.
[01:36.04]But they noted that additional research is needed
[01:40.40]to confirm a history of microbial life.
[01:44.96]The examinations did suggest
[01:48.32]the rock contains "organic compounds,"
[01:52.20]NASA said.
[01:53.80]But the statement added,
[01:55.84]"While such carbon-based molecules
[01:58.48]are considered the building blocks of life,
[02:01.92]they also can be formed
[02:04.24]by non-biological processes."
[02:07.68]Perseverance uses its robotic arm
[02:11.64]and drilling equipment to capture rock
[02:14.92]and soil samples from the Martian surface.
[02:19.20]So far, it has collected 22 samples.
[02:23.76]The rover has secured the samples in special containers
[02:28.44]and they are to be picked up and returned to Earth
[02:32.68]during a future mission.
[02:35.44]Ken Farley is a project scientist
[02:38.80]with the Perseverance team
[02:41.04]at Caltech in Pasadena, California.
[02:44.76]He said, "Cheyava Falls is the most puzzling,
[02:49.44]complex, and potentially important rock
[02:53.44]yet investigated by Perseverance."
[02:57.08]Farley said unusual color spots
[03:00.60]and other structural elements in the samples
[03:03.96]suggest "chemical reactions"
[03:06.92]that might have given energy
[03:09.36]to ancient microbial life.
[03:12.24]But he noted that so far, scientists
[03:16.16]have not been able to identify
[03:18.84]exactly how the rock formed.
[03:21.76]The team described the rock
[03:24.80]as containing white veins
[03:27.60]that may have been created
[03:29.56]by the substance calcium sulfate.
[03:32.88]Between the veins, examiners found
[03:36.00]lines of material with a reddish color.
[03:39.52]These lines suggest the presence of hematite,
[03:44.32]a common substance found in many rocks on Earth.
[03:49.00]David Flannery is an astrobiologist
[03:53.00]and member of the Perseverance science team
[03:57.00]from the Queensland University of Technology in Australia.
[04:02.68]He said that on Earth,
[04:04.84]these kinds of rock elements are often linked
[04:08.64]"with the fossilized record of microbes
[04:12.20]living in the subsurface."
[04:14.76]The scientists said the new findings
[04:18.52]strengthen existing evidence
[04:21.12]that such rocks may have been created
[04:24.16]or were changed by flowing water on Mars
[04:28.28]billions of years ago.
[04:30.56]Caltech's Farley said the rock sample
[04:34.44]had already been imaged
[04:36.60]and examined with lasers, X-ray equipment
[04:40.72]and other instruments
[04:42.40]as much as possible in recent weeks.
[04:45.84]He noted that Perseverance
[04:48.40]has done as much as it can
[04:50.72]to examine the newly discovered samples.
[04:54.28]Farley added, "To fully understand
[04:57.80]what really happened in that Martian river valley
[05:01.52]at Jezero Crater billions of years ago,
[05:05.32]we'd want to bring the Cheyava Falls
[05:08.56]sample back to Earth."
[05:10.76]That way, he said,
[05:13.08]"it can be studied with the powerful instruments
[05:16.88]available in laboratories."
[05:19.52]I'm Bryan Lynn. 更多听力请访问21VOA.COM
END OF TRACK. "END OF TRACK." The two men bowed. "Whoever was that person you were talking to?" she enquired, as soon as they stood together. The took of triumph faded from her eyes, she had grown worn and weary. The roses were wilting on the walls, the lights were mostly down now. Hetty, looking in to see if anything was wanted, found herself driven away almost fiercely. I only saw Master Jervie once when he called at tea time, The year 1747 was opened by measures of restriction. The House of Lords, offended at the publication of the proceedings of the trial of Lord Lovat, summoned the parties to their bar, committed them to prison, and refused to liberate them till they had pledged themselves not to repeat the offence, and had paid very heavy fees. The consequence of this was that the transactions of the Peers were almost entirely suppressed for nearly thirty years from this time, and we draw our knowledge of them chiefly from notes taken by Horace Walpole and Lord Chancellor Hardwicke. What is still more remarkable, the reports of the House of Commons, being taken by stealth, and on the merest sufferance, are of the most meagre kind, sometimes altogether wanting, and the speeches are given uniformly under fictitious names; for to have attributed to Pitt or Pelham their[112] speeches by name would have brought down on the printers the summary vengeance of the House. Many of the members complained bitterly of this breach of the privileges of Parliament, and of "being put into print by low fellows"; but Pelham had the sense to tolerate them, saying, "Let them alone; they make better speeches for us than we can make for ourselves." Altogether, the House of Commons exhibited the most deplorable aspect that can be conceived. The Ministry had pursued Walpole's system of buying up opponents by place, or pension, or secret service money, till there was no life left in the House. Ministers passed their measures without troubling themselves to say much in their behalf; and the opposition dwindled to Sir John Hinde Cotton, now dismissed from office, and a feeble remnant of Jacobites raised but miserable resistance. In vain the Prince of Wales and the secret instigations of Bolingbroke and Doddington stimulated the spirit of discontent; both Houses had degenerated into most silent and insignificant arenas of very commonplace business. "It certainly will be. Miss Widgeon," answered Maria, with strictly "company manners." "One who has never had a brother exposed to the constant dangers of army life can hardly understand how glad we all feel to have Si snatched from the very jaws of death and brung back to us." "Just plug at 'em as you would at a crow, and then go on your way whistlin'?" persisted Harry. "Hurroo!" echoed Hennessey; "that's the ticket." "Come forward, keeper," continued the baron, "and state how these arrows came into your hands!" "Yes." HoMEJULIA京香2018下载
ENTER NUMBET 0015www.buur.com.cn
www.38464.com.cn
815151.com.cn
yzhi432.com.cn
qimeimei.com.cn
bolj.com.cn
www.mynovel.net.cn
dorain.com.cn
bodcep.com.cn
2050132.com.cn