全火星地下水系统的首个证据

WatersofMars二十年以前,火星曾经是否有过大量储存的液态水的问题依然备受争议。当前,这个讨论变成了对自然和液态水的体积的评估,例如液态水在哪里以及对于在火星上寻找生命(或生命留下来的物质)的努力有什么暗示。欧洲空间局的科学家们已经公布了火星快车对一些位于火星北半球的封闭的坑洞的观测结果。

作为作家中的领袖和荷兰的乌德勒支大学弗兰克林·萨莱斯说道:“早期的火星是一个充满水的世界,但是当该行星扥气候变化时,这些水从地表退回来了,形成了‘地下水 ’和水池。由于水的规模和角色还存争议,因此在这个研究中,我们记录了这些水,而且我们寻找到了火星上首个全星球的地下水系统的地质的证据。”

在从4000米到4500米深的范围内,被撞击出的坑洞的底部显示了只有水的存在下才会形成的特征。变化的深度的发现说明随着时间的变迁,水的高度改变了,并且渐渐降低。

GlobalGroundwater

坑洞中水的高度与人们所猜想的火星海洋里被提议的水的高度在一条直线,这证明了一个位于北方大平原(显示在上面的图中)的全球性大洋曾经覆盖火星北半球的三分之一。另外一种猜测也是可能的,就是至少两个覆盖全球的大洋在不同时期出现过——一个是连绵而辽阔的,存在于这颗行星早期时,另一个是更小、更浅的、不连续的(或者是河湖系统),有可能在大量火山作用或其他地热的活动加热了受困于地表以下的冰块时短时间地存在过。

火星上的地下水系统的存在可与这些假说兼容。火山口湖通过和我们在地球上看到的相同的地下水系统相互联系在一起。这个共同点是为什么我们相信火星长期地拥有显著的液态水的一个主要因素。我们已经找到了一些岩石,这些岩石在地球上的形成依靠液态水的存在和说明水力驱动侵蚀的地形的大规模特征,而水力驱动侵蚀的地形和液态水的存在曾经对改变火星的地貌景观有显著的作用。

在火星的古代时期转变到赫斯珀里亚时期后,这种活动迅速减少,而赫斯帕里亚时期也是火星被相信已经变得比以前干旱很多的时间。挪亚时代后的亚马逊河时期的特点是寒冷,这是现在仍然影响并支配这个星球的寒冷的火星环境。

已知的是大量的冰仍旧存在于这颗行星的北极,一个湖泊被相信依旧残留在南极的冰盖下面,这个湖泊和地球上南极洲中数英里冰层底下 的液态湖相似。任何依然存在于火星上的液态水在这个时候可能被更好地描述成“在火星里”。液体的痕迹会在地表偶尔出现,但是曾经却没有观测到大量的自由流动的水。

相同的团队也发现了5个特定的坑洞,在这几个坑里含有对于地球上生命的起源很普遍的矿物质,包括各种各样的黏土、碳酸盐与硅酸盐。这种流域有可能成为寻找火星上曾经可能存在的生命的主要位置。

本文来源于:

First Evidence of Global Groundwater System Found on Mars

Twenty years ago, the question of whether Mars ever had large reserves of liquid water was still open to debate. Today, the discussion has shifted to an evaluation of the nature and size of those reserves, where they existed, and what this implies for any effort to find life (or the remains of it) on the Red Planet. Scientists with the European Space Agency have released the results of Mars Express’ observation of some 24 deep, enclosed craters in the northern hemisphere of Mars.

“Early Mars was a watery world, but as the planet’s climate changed this water retreated below the surface to form pools and ‘groundwater,’” says lead author Francesco Sales of Utrecht University in the Netherlands. “We traced this water in our study, as its scale and role is a matter of debate, and we found the first geological evidence of a planet-wide groundwater system on Mars.”

The floor of the impact craters showed features that could only have formed in the presence of water, at depths ranging from 4,000 to 4,500 meters. The various depth findings show that the water level changed and receded over time.

The water level in the craters aligns well with the proposed water level in the Mars ocean hypothesis, which argues that a global ocean situated in the Vastitas Borealis (pictured above) once covered the northern third of Mars. It’s also possible that at least two global oceans existed on Mars at different points — one vast and persistent, during the earliest days of the planet, and a smaller, shallower, and less-persistent ocean (or system of rivers and lakes) that may have temporarily existed when vast amounts of volcanism or other geothermal activity heated ice trapped below ground.

The existence of a groundwater system on Mars is compatible with these hypotheses. Crater lakes would have attached to each other through the same types of groundwater systems we see on Earth. Such commonalities are a major component of why we believe Mars supported significant amounts of liquid water for long periods of time. We’ve found rocks whose formation on Earth depends on the presence of liquid water and large-scale features of the terrain that indicate water-driven erosion once played a significant role in weathering the Martian landscape.

The incidence of such activity drops off sharply after Mars’ Noachian period transitions into the Hesperian, which is also when Mars is believed to have become much drier. The Amazonian period that followed the Noachian is characterized by the cold, arid Martian conditions that still dominate the planet today.

Substantial amounts of ice are known to still exist at the planet’s north pole, and a lake is believed to still remain beneath the south polar ice cap, similar to the liquid lakes under miles of ice in Antarctica on Earth. Any liquid water still existing on Mars might be better described as being in Mars at this point, given the depths at which it would be located. Traces of liquid are occasionally found at the surface, but no significant amount of free-running water has ever been observed.

The same team also spotted five specific craters where mineral ingredients believed to be common to the rise of life on Earth also exist, including various clays, carbonates, and silicates. Such basins could be prime locations for searching for the life that may have existed on Mars.

由于尘埃降落到在火星上,机遇号漫游者仍然是失踪的。

         由于操控者正在准备发起联系,因此这个漫游者还没有报到。Opportunity rover still MIA as dust settles on Mars

我们在火星上看到的最大的一次沙尘暴现在正在逐渐结束,给机遇号将快速得到足够的功率 去重新开启和地球的正常联系带来了希望。从六月至今,这个漫游者已经失去了联系,控制者也在准备好去尝试使漫游者回复NASA的深空探测网发送的命令。

和更大的好奇号漫游者不同,机遇号由太阳能供电。当现在的沙尘暴渐渐包围了整个火星的大气层时,为它提供能量的太阳光逐渐变淡。机遇号已经有几个月不能够得到足够的能量去维持在正常的功能,导致它转换到了休眠模式。一旦它经历了这次在6月的转换,这个漫游者就有了足够的功率和地球上的操作人员实现应答了。

基于大气层的状况,那些操作人员预测在不久的未来那个电源很有可能是充足的。可是,这个漫游者的情况会有一些无法把握的事情,这意味着它将不会像预期的那样进行联系。最简单的可能是沙尘暴在漫游者的太阳能控制板上沉积了足够的尘埃,使它一直远离充足电量的程度。那能够把它从睡眠的返回推延到最后一颗尘埃离开大气层,或者甚至造成电量停留在低的状态,直到附近的风清理了控制板。

当然,那一切假设每件事情都在正常地运行。机遇号的电量很有可能降得太低了,以至于它的机载时钟停止运转。如果是那种情况,那么就没有方法去得知这个漫游者什么时候会努力重新连接建立联系。这是操作人员正在准备给它发送命令去建立联系的缘故之一,到了那时就不能等待漫游者去应答了。

在休眠的过程中,一些电量或联络的硬件设备也有可能出故障了。操作者认为漫游者现在待着的位置会保持足够温暖,能使一些主板上加热器将继续维持部件在被估计的温度或其以上,所以问题基本上是部件是旧的而且它们已经在火星上的14年的条件是艰苦的。

在状况好到能使它产生足够的功率以回应后,NASA将持续尝试去联络漫游者45天。如果在那个时段里没有响应,漫游者的操控者将只会再用几个额外的月份来被动地听它。

Opportunity rover still MIA as dust settles on Mars

The rover has not checked in as controllers are getting ready to trigger contact.

One of the largest dust storms we’ve ever seen on Mars is finally winding down, raising hopes that the Opportunity rover will soon be able to obtain enough power to resume normal contact with Earth. At this point, there’s been no contact with the rover since June, and controllers are getting ready to attempt to get the rover to respond to commands sent over NASA’s Deep Space Network.

Unlike the larger Curiosity rover, Opportunity is solar-powered. And as the current dust storm gradually grew to encompass the entirety of Mars’ atmosphere, the sunlight that powered it gradually faded out. For several months, Opportunity hasn’t been getting enough powerto maintain normal function, causing it to shift into a hibernation mode. Once it underwent this shift back in June, the rover has been waiting for enough power to start checking in with its operators here on Earth.

Based on the atmospheric conditions, those operators expect that power is likely to be sufficient in the very near future. There are a number of uncertainties regarding the rover’s condition that could mean it won’t be making contact as expected, however. The simplest possibility is that the storm deposited enough dust on the rover’s solar panels to keep them from reaching sufficient power levels. That could delay its return from hibernation until the last of the dust is out of the atmosphere, or it could even cause the power to stay low until local winds clean the panels off.

All that, of course, assumes everything’s working normally. There’s a good chance that Opportunity‘s power dropped so low that its on-board clock shut down. If that’s the case, then there’s no way of knowing when the rover will try to re-establish contact. That’s one of the reasons that operators are preparing to send it commands to establish contact rather than waiting for the rover to try to check in.

There’s also the chance that some power or communication hardware failed during the hibernation. Operators expect that the location the rover is in will stay warm enough that some small onboard heaters will keep components at or above the temperatures they’re rated for, so the issue is primarily that the components are old and the conditions have been harsh for the 14 years they’ve been on Mars.

NASA will continue attempts to contact the rover for 45 days after the conditions are good enough for it to generate sufficient power to respond. If there’s no response during that period, the rover’s controllers will just passively listen for it checking in for several additional months.

NASA的洞察号着陆器正在红色行星上正式地开展搜寻地震的工作

This image from NASA's InSight Mars lander, taken on Jan. 7, 2019, shows the SEIS seismograph instrument deployed on the Martian surface to measure Marsquakes.

根据建造此地震仪的法国航天局的说法,这个用于叫做SEIS的内部结构地震实验的超级灵敏地震仪已经通过了最初的实验,目前工作正常。

“这是一个具有历史意义的时刻,也是地球物理学重大的希望,”法国航天局的官员正式说道。“美国的NASA在1975年发射的海盗1和海盗2航天飞船上都带着一个地震仪。其中的一个地震仪的功能失效,另一个地震仪安装在舱面上,由于它对风产生的周围的背景噪声过于敏感而没能检测到火星的震动。SEIS是此类仪器中第一个被放置在火星地表上的。”

洞察号着陆器于11月26日在火星上登陆。12月19日,它用像起重机的机器手臂使SEIS在火星的地表上展开。洞察号将迅速地在SEIS地震仪上面安装一个特殊的盖子覆盖住SEIS地震仪之上,以使它免受火星上的风和极端的温度的侵扰。

法国航天局的官员说道,自从NASA的阿波罗17号在月球上登陆后宇航员哈里森·施密特有效地利用那次任务的阿波罗月球表面实验包——一个含有月球地震仪的传感器组件以来,SEIS是第一个开始在另一个世界里成功地开始工作的地震仪。

SEIS由三个钛球体中的超静谧的振动传感器组成,被置于真空中。一个用来给它的系统供电的电子拴绳和加热器在1月6日被配置好。根据法国航天局,SEIS传感器“正在开始记录每分钟的地面移位”。

洞察号的SEIS是这个着陆器将要调动的两个工具中的一个。另外一个是用来挖掘的一个工具,叫做具有热流和物理特性的探头,或者HP3。执行航天任务的科学家们将要利用敏感的地震仪去检测火星震和陨石的撞击、研究火星内部的结构;利用HP3记录着关于热量如何在这个星球的地表里移动的。为了帮助科学家们研究这个行星的震动,洞察号也要做一个无线电实验。

NASA在2018年5月份发射了85千万美元的洞察号着陆器(它的名字是使用地震勘探、测地学和热量转移的简称)。人们期待它能用至少一个火星年——大约两个地球年的时间来研究火星的内部。

NASA’s InSight Lander on Mars Is Now Hunting for Marsquakes

This image from NASA’s InSight Mars lander, taken on Jan. 7, 2019, shows the SEIS seismograph instrument deployed on the Martian surface to measure Marsquakes.

NASA’s InSight Mars lander is officially hunting for quakes on the Red Planet.

The lander’s ultrasensitive seismometer, called the Seismic Experiment for Interior Structure (SEIS), has passed its initial tests and is working working well, according to the French space agency CNES, which built the lander’s instrument.

“This is a historic moment and a great hope for geophysics,” CNES officials said in a statement. “The two U.S. Viking 1 and Viking 2 missions launched by NASA in 1975 were each carrying a seismometer. One failed to function, while the other — fixed to the deck of the lander — was unable to measure Mars’ seismic activity as it was too sensitive to the background noise generated by winds. SEIS is thus the first instrument of its kind to be placed on the surface of the Red Planet.” [NASA’s InSight Mars Lander: Full Coverage]

The InSight lander touched down on Mars Nov. 26 and used its crane-like robotic arm to deploy the SEIS instrument on the Martian surface on Dec. 19. On Jan. 1, InSight celebrated the new year by testing the seismograph, CNES officials said. InSight will soon deploy a special cover over the SEIS instrument to protect it from the Martian wind and extreme temperatures.

SEIS is the first seismometer to successfully begin work on another world since NASA’s Apollo 17 moon landing in 1972, when astronaut Harrison Schmitt deployed a that mission’s Apollo Lunar Surface Experiments Package — a sensor suite that included a lunar seismometer, CNES officials said. SEIS is made up of three ultraprecise seismic sensors surrounded by a vacuum inside a titanium sphere. An electronic tether to power its systems and heaters was deployed on Jan. 6, and the SEIS sensors “are beginning to record minute ground displacements.” according to CNES.

InSight’s SEIS instrument is one of two tools the lander will deploy on the surface of Mars. The other is a burrowing tool called the Heat Flow and Physical Properties Probe, or HP3. Mission scientists will use the sensitive seismometer to detect Marsquakes, meteorite impacts and to study the structure of the interior of Mars, with the HP3 tool recording observations on how heat moves through the planet’s surface. InSight also carries a radio experiment to help scientists study the planet’s wobble.

NASA launched the $850 million InSight lander (its name is short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) in May 2018. It is expected to study the interior of Mars for at least one Martian year, which is about the equivalent of two Earth years.

NASA的火星好奇号着陆器发现关于神秘的夏普山的证据。

通过对好奇号的一个航行工具进行改进,科学家们已经分析了着陆器下面的岩石的密度,发现它的孔隙度原来所想的要更大。

一个科考队设法改变了一个监测运动状况的设备的用途,该设备帮助NASA的好奇号漫游者导航,它被改造后应用于测量这颗红色行星重力场的变化范围。在这个过程中,科学家们发现着陆器底下的岩石比原来认为的要有更多的小孔。这提供了神秘的夏普山的形成的一些证据,夏普山是一个奇异的山丘,该着陆器一直在盖尔陨坑的中央探索它。

“这个研究有一点像此类型中的第一个。”霍普金斯大学研究报告的作家凯文路易斯说道。“它是在地球和月球之外另一个的行星中第一个引力测线。

在地球上,地质学家通常用这类仪器来研究潜藏在地下的岩石。但是在火星上,研究者只能从绕轨道飞行的航天飞船上获得这种重力的数据,由于航天飞船离火星地表太远而不能拍摄到一张精细的图像。所以即使好奇号漫游者已经在这颗红色星球上待了六年多了,科学家和工程师们一起工作,主要给好奇号提供一个新的仪器。

就像路易斯解释的一样,引力只不过是加速度。好奇号配备有加速计——就像用在苹果手机和其他电子产品上面常用的加速度一样——既可以用来航行,也可以用来得知车的方向。因此,通过使用着陆器的加速计,这个团队能够测量来自各处地下岩层的重力“牵引”。

从亚丽桑大立州大学毕业的一个队员特拉维斯加布里埃尔在一封电子邮件中说道:“引力的测量……给这个行星上一块特别的区域提供一个放大镜。这就是地表上重力的测量在地球地质的工具腰带中是一个主要工具的原因。”所以,通过将好奇号发送去爬位于火星的盖尔陨坑中间一个高3英里(高5公里)的夏普山,这个团队能够发现这个地区的密度以及夏普山在过去是怎样的形成的。

在过去,研究者们认为盖尔陨坑的底部在很久以前有可能埋藏在数英里的岩石下面。

“如果你在月亮上用一个望远镜观察火星,你会注意到在大多数大型坑洞中央的小山峰——盖尔陨坑也是一样的。但是盖尔陨坑中的山峰比个的边缘要更高。这导致科学家们相信他曾经一次性地充满沉积物。”

因此,当好奇号的重力数据表明这个想法是根本不可能的时候,人们都极其惊讶。这是因为即使那里石头的密度极其小,它里面实际的矿物质很稠密。这意味着岩石中充溢着使其变得多孔的空洞。

如果盖尔陨坑曾经被充溢到边缘上,那么就像路易斯所说的那样,样式中的孔隙就会在数吨的石头下面,基本上被挤扁。

加布里埃尔补充说:“我们现在认为盖尔陨坑只是部分地被充满了,引出了‘盖尔陨坑的历史以及远古时期火星赤道上的环境状况是怎样的’这个谜团。”与之不同的是,这个团队认为在更暖和的时候,风可能已经把残骸吹到坑里;在寒冷的夜晚中,风又使残骸被吹到坑外,在数百万年里逐渐形成夏普山。

这可能不将是我们最后一次听到好奇号“新”的重力设备。“在我们的分析中,我们也证实了这个加速计检测火星上的地震的能力,这又是在此类尺度上的又一次科技演示,并可以在未来对火星的地表下面提供全新的洞察力。”加布里埃尔补充道。

这个研究将会于2月1日(周五)发表在杂志《科学》中。

本文来源于:

NASA’s Mars Curiosity rover finds clues about mysterious Mount Sharp

By tweaking one of Curiosity’s navigational tools, scientists have analyzed the density of the rock beneath the rover, finding it’s more porous than previously thought.
curiosity1

This 2016 Curiosity rover selfie shows the vehicle at the “Okoruso” drilling site on Mount Sharp’s Naukluft Plateau. The Martian scene is a mosaic of images taken with the arm-mounted Mars Hands Lens Imager (MAHLI).

A team of researchers managed to repurpose a movement-detecting device that helps NASA’s Curiosity rover navigate and use it to measure variations in the Red Planet’s gravitational field. In the process, the scientists discovered that the rocks beneath the rover are more porous than previously suspected. This offers clues into the mysterious formation Mount Sharp, a strange hill the rover has been exploring in the center of Gale Crater.

“This study is a little bit of the first of its kind,” said study author Kevin Lewis of Johns Hopkins University. “It’s the first gravity traverse on the surface of another planet other than the Earth and the moon.”

On Earth, geologists commonly use such instruments to study rocks lurking beneath the surface. But on Mars, researchers could only get this kind of gravity data from orbiting spacecraft, which are too far away to get a detailed picture. So scientists and engineers worked together to essentially give Curiosity a new scientific instrument — even after more than six years on the Red Planet.

As Lewis explains, gravity is really just acceleration. And Curiosity is equipped with accelerometers — like the ones commonly used in iPhones and other electronics — which are used both to drive and get the vehicle’s orientation. So, by using the rover’s accelerometers, the team was able to measure varying gravitational “tugs” from subsurface rock layers.

“Gravity measurements … provide a magnifying lens into one particular area of the planet’s subsurface,” Travis Gabriel, a team member and graduate student at Arizona State University, said in an email. “This is why surface measurements of gravity are a staple tool in an Earth geologist’s toolbelt.” So, by sending Curiosity to climb Mount Sharp, a 3-mile-tall (5-km-tall) mountain in the middle of Mars’ Gale crater, the team was able to uncover the density of the area’s rocks and how Mount Sharp likely formed.

Martian geology

In the past, researchers thought the floor of Gale Crater was probably buried beneath miles of rock long ago.

“If you look through a telescope at the moon, you’ll notice central peaks in most of the large craters – Gale Crater is no different,”Gabriel said. “However, (Gale’s) central peak stands taller than the crater’s rim, which leads scientists to believe it was filled to the brim with sediments at one time.”

So it came as a surprise when Curiosity’s gravity data showed this idea just isn’t possible. That’s because the rocks there have a surprisingly low density, even though the actual minerals in the rocks are fairly dense. This implies the rocks are riddled with empty pockets that make them porous.

If Gale Crater had ever been filled to the brim, those pores in the rocks would have been essentially “squished out,” as Lewis put it, beneath tons of rock.

“We think Gale Crater was filled only partially, providing a critical piece of the puzzle that is the history of Gale crater and the ancient environmental conditions at the equator of Mars,” Gabriel added. Instead, the team suggests winds may have blown debris into the crater in the warmer day hours and out of the crater during the cold night, gradually forming Mount Sharp over many millions of years.

And this probably won’t be the last time we hear about Curiosity “new” gravity instrument. “In our analysis, we also demonstrated the capacity of the accelerometers to measure martian earthquakes, which is yet another technology demonstration with these units and can provide new insights in the subsurface of Mars in the future,” Gabriel added.

The research will be published in the journal Science on Friday, Feb. 1.