Mars on Earth: soil analogues for future Mars missions

Exploring Mars would be easier if researchers knew more about the properties and behaviour of martian soils. Jeffrey J Marlow, Zita Martins and Mark A Sephton explain how terrestrial analogues could help – especially if we had more of them.     

Sunspots and Mars frost

Peter Bond discusses the latest observations of the Sun and Mars and the possibilities for a Pluto mission, among other space news.     

单程波叠前深度偏移中的界面深度问题研究

单程波深度偏移计算中,两条主要因素影响到反射层的正确定位,一是算子带来的子波相位变化,二是炮点子波脉冲延迟.本文首先r推导了单程波算子导致的相位变化,并且介绍了一种比水平反射层模型偏移验证方法更简单的脉冲叠加验证方法,并用该方法用脉冲试验对比了单程波偏移相位的变化和改正后的结果,子波延迟导致的反射层深度的变化和改正后结...     

Diffraction imaging in depth

High resolution imaging is of great value to an interpreter, for instance to enable identification of small scale faults, and to locate formation pinch-out positions. Standard approaches to obtain high-resolution information, such as coherency analysis and structure-oriented filters, derive attributes from stacked, migrated images. Since they are image-driven, these techniques are sensitive to artifacts due to an inadequate migration velocity; in fact the attribute derivation is not based on the physics of wave propagation. Diffracted waves on the other hand have been recognized as physically reliable carriers of high- or even super-resolution structural information. However, high-resolution information, encoded in diffractions, is generally lost during the conventional processing sequence, indeed migration kernels in current migration algorithms are biased against diffractions. We propose here methods for a diffraction-based, data-oriented approach to image resolution. We also demonstrate the different behaviour of diffractions compared to specular reflections and how this can be leveraged to assess characteristics of subsurface features. In this way a rough surface such as a fault plane or unconformity may be distinguishable on a diffraction image and not on a traditional reflection image.
We outline some characteristic properties of diffractions and diffraction imaging, and present two novel approaches to diffraction imaging in the depth domain. The first technique is based on reflection focusing in the depth domain and subsequent filtering of reflections from prestack data. The second technique modifies the migration kernel and consists of a reverse application of stationary-phase migration to suppress contributions from specular reflections to the diffraction image. Both techniques are proposed as a complement to conventional full-wave pre-stack depth migration, and both assume the existence of an accurate migration velocity.     

From Mars to M81

Martian dust, erosion on Callisto, interstellar gas and the solar wind all play their part in this issue's round-up of space science from Peter Bond .     

Mars: simply red?

Ernst Hauber and Gerhard Neukum present a new perspective on the martian surface on the basis of two years of observations by the High resolution Stereo Camera, part of ESA's Mars Express mission.
All HRSC images shown are copyright ESA/DLR/FU Berlin (G Neukum).     

Mars as never seen before

Images from the High Resolution Stereo Camera on Mars Express reveal the surface of the Red Planet in unprecedented detail – and should have the whole planet mapped at high resolution in just two years. Over the next six pages, Ernst Hauber and Gerhard Neukum set the scene and reveal some of the spectacular images already captured.
(All images are courtesy of ESA/DLR/FU Berlin/G Neukum unless otherwise credited.)     

美国火星探测的进展

美国国家航空与航天管理局(NASA)的“勇气号”火星探测器于美国太平洋时间2004年1月3日20时35分(北京时间4日12时35分)成功着陆于火星的“古谢夫环形山”。为此，美国“火星探测流浪者”项目引起了举世的关注。     

Interaction of the solar wind with Mars from Mars Global Surveyor MAG/ER observations

The observations of the magnetometer/electron reflectometer (MAG/ER) investigation onboard the Mars Global Surveyor (MGS) have greatly contributed to improve our understanding of the interaction of the solar wind with Mars. These observations established conclusively that a global dynamo-generated magnetic field does not exist at Mars, and that the interaction with solar wind is of the atmospheric type. This article reviews the most important results obtained from MGS MAG/ER on the study of two major features in the Mars solar wind interaction. The first feature is the occurrence of large-amplitude, highly coherent waves at the proton cyclotron frequency in the region upstream from the Martian bow shock. The second feature is the magnetic pileup boundary (MPB), a well-defined plasma boundary inside of which the planetary exospheric ions outnumber the solar wind ions. The study of these two elements is crucial to characterize the properties of the Martian exosphere. In addition, the occurrence of an MPB at comets and Venus reveals common processes to all these unmagnetized atmospheric bodies in spite of their different physical nature and characteristic scales.     

深度震相sSmS特征及其在震源深度确定中的应用

通过一系列理论地震图模拟,研究了莫霍面超临界反射深度震相sSmS的特征,分析了影响该震相的各种因素。结果表明,SmS和sSmS属于高频波,一般情况下在高频段(1Hz左右)可被清晰地观测到;而在更长周期的地震图上,SmS和sSmS的强度比S波或者S多次波弱,不易辨认;地壳结构复杂地区且震源深度较浅时,sSmS震相也不容易被观测到。本文以2011年6月20日腾冲MS5.2地震为研究实例,利用sSmS深度震相确定其震源深度为6km,与其它方法所得结果一致。在利用深度震相测定震源深度的研究中,sSmS震相可以作为震源深度精确测定的手段之一。     

Hello Mars, goodbye Hubble?

Successes at Mars make the promise of more money for space exploration appealing, but will other projects pay the price? Peter Bond reports.     

Mars: a geologically active planet

Karl L Mitchell and Lionel Wilson summarize the case for martian geological activity in recent times.     

Quasi-stationary planetary waves in the middle atmosphere of Mars

Using the temperature profiles retrieved from the Mars Climate Sounder(MCS) instrument onboard Mars Reconnaissance Orbiter(MRO) satellite between November 2006 and April 2013, we studied the seasonal and interannual variability of QuasiStationary Planetary Waves(QSPWs) in the Martian middle atmosphere. The QSPW amplitudes in the Southern Hemisphere(SH) high latitudes are significantly stronger than those in the Northern Hemisphere(NH). Seasonal variation with maximum amplitude near winter solstice of each hemisphere is clearly seen. The vertical structure of the QSPW in temperature shows double-layer feature with one peak near 50 Pa and the other peak near 1 Pa. The QSPW in geopotential height is clearly maximized in the region between two temperature peaks. The maximum amplitude of QSPW for s=1 is ~8–10 K in temperature and ~1 km in geopotential height in the SH high latitudes. The maximum amplitude at the SH high latitudes in Mars Year(MY) 31 is ~2 K stronger than those in other MYs, suggesting the clear interannual variability. We compared the satellite results with those obtained from the Mars Climate Database(MCD) simulation version 5.0; a reasonable agreement was found. The MCD simulation further suggested that the variability of dust might partially contribute to the interannual variability of QSPW amplitude.     

Advances in automated detection of sand dunes on Mars

This paper describes advances in an automatic approach for the detection of sand dunes of Mars, based on supervised learning techniques. A set of features (gradient histogram) is extracted from the remotely sensed images and two classifiers (Support Vector Machine and Random Forests) are trained from this data. The evaluation is conducted on 230 MOC‐NA images (spatial resolution between 1·45 and 6·80 m/pixel) leading to about 89% of correct detections. A detailed analysis of the detection results (dune/non‐dune) is performed by dune type or bulk shape, confirming high performances independently of the way the dataset is analysed. This demonstrates the robustness and adequacy of the automated approach to deal with the large variety of aeolian structures present on the surface of Mars. Copyright © 2012 John Wiley & Sons, Ltd.