Hermes Global Orbiter: A Discovery mission in gestation

Several missions are planned which should deposit on Mars a number of landers that will perform detailed observations of the planet's surface, subsurface and atmosphere. The CNES Netlander mission aims at establishing a network of 4 geophysical stations. They will offer a unique opportunity to explore the interior of Mars, its subsurface, atmosphere and ionosphere from 4 landing sites representing different geophysical conditions. One of the most important objectives is the investigation of the underground geological entities and the search for water reservoirs in the form of ground ice or even liquid water. The GPR experiment on Netlander, Berthelier et al. (2000), Ney et al. (2002), Ciarletti et al. is a ground penetrating radar that has been proposed to perform such observations. It is based on a new concept that will allow to explore the subsurface from a fixed position with the goal of achieving a 3D imaging of the underground. Features of instrumentation are discussed.

The Russians and the Americans are shooting at a common target, yet neither can see it and at least one shooter hopes to miss it completely. The Soviet projectile is Venus 4, a space probe that beat the U.S. Mariner 5 into space by two days in the middle of last month. Both spacecraft are bound for earth's mysterious sister planet Venus, both should arrive some time in October, and both represent attempts to settle one of the biggest planetary controversies ever waged. The Russian probe is so much larger than Mariner-it weighs more than 2,400 pounds compared to Mariner's 540-that it may even be two spacecraft in one, with a secondary capsule to land on the planet's surface while the parent vehicle flies by. Mariner 5 carries instruments to measure Venus' magnetic field, to pierce its atmosphere with radio waves, to hunt for hydrogen and oxygen in its upper atmosphere and to examine the space around it for radiation, charged particles and the solar wind. Yet all this information will be but a drop in the virtually empty bucket of information on earth's nearest neighbor outside the moon. Cloaked in a seemingly impenetrable blanket of clouds-and recently doubt has been cast even on thatVenus has intrigued and defied astronomers for centuries. The first photographs of the planet that showed even any shading were taken in 1911, and Venus has yet to be revealed as anything more distinct than a smudge. The noted British astronomer Patrick Moore spent 30 years studying vague visible shadings on Venus, looking for a clue to the hidden planet's period of rotation, but in vain. Fairly accurate estimates, however, have been made by other methods. Until 1964, the best guess at the rotation period was about 266 earth days. but that estimate, made by scientists at California's Jet Propulsion Laboratory, was accurate only to within four weeks either way. Then the huge radio telescope at Arecibo, Puerto Rico, was used to bounce radio waves off the planet's surface; Cornell researchers measured the Doppler shift of the returning waves to pin down the period at 253 days, plus or minus five days. The direction of the shift also confirmed the suspicion that Venus rotates in the opposite direction from the earth and all the other planets in the solar system except Uranus. A year later, radar measurements refined the number to 247 days, give or take five. In 1966 it was suggested that earth itself played a hand in Venus' rotation. Drs. Peter Goldreich and Stanton J. Peale of the University of California said that earth's gravity was enough to cause the same side of Venus to be facing the earth every time the two planets were lined up with the sun. If that were true, the rotation period of the planet would be 243.16 days. Only two months later, measurements at JPL confirmed the time, trimming off a half-day to compensate for an electronic error in the equipment, leaving a final estimate of 242 days 14 hours and 24 minutes. Few if any other Venusian details have been settled upon with such accuracy, however. One summary of Venus research, prepared for the National Aeronautics and Space Administration, observes with considerable understatement that there is uncertainty about the abundance of carbon dioxide in the planet's atmosphere: recent estimates range from four to 90 percent. The atmosphere of the planet, in fact. is its most discussed feature, since it has much to do with most of Venus' other characteristics-temperatures. winds, surface features, even the possiblility of life. Venus is indeed a near twin to earth, and the similarities of the planets themselves are largely responsible for the similarities, however disputed, of their atmospheres: Venus' density is about .934 times that of earth, its diameter .956 times that of earth, and the speed required to escape from its gravity .913 times that of earth. As a result, Venus is much more able than, say, Mars, which is smaller and has about a third of earth's gravity, to retain an atmosphere with gases as light as those on earth. This does not mean that our sister planet's atmosphere is the same as earth's, however. The air we breathe is about four-fifths nitrogen, with oxygen comprising almost all of the remainder; hydrogen, carbon dioxide and miscellaneous other gases make up the rest. An estimate of Venus' atmosphere is difficult with so many conflicting studies, but the NASA summary makes a reasonable attempt: the major constituent is again nitrogen. perhaps 63 percent; the next 31.5 percent is neon. based on the relative abundances of gases in the sun, minus the helium and hydrogen which would have escaped from the planet's weaker gravity; for carbon dioxide the report allows about 5 percent; with water, oxygen and all the other gases and vapors making up the remaining half percent. Water is a sore point with Venus researchers. As a key factor in the life-or-not controversy, it has scientists lined up in opposing camps. Typical of one side is Dr. John Strong, director of Johns Hopkins University's Astrophysics and Physical Meteorology Laboratory in Baltimore, Md., who in 1964 sent a spectrometer up 17 miles in a balloon to study the light reflected from Venus' clouds. His finding, Lowell Observatory

Possible consequences of collisions of natural cosmic bodies with the Earth’s atmosphere and surface are described. The methodological basis of classification of consequences is the solution of meteor physics equations characterizing the trajectory of a body in the atmosphere, namely, the dependence of the body’s velocity and mass on the flight altitude. The solution depends on two dimensionless parameters characterizing the drag altitude and the role of mass loss by a meteoroid during its motion in the atmosphere. Depending on values of these parameters, the degree of effect on the planetary surface considerably changes. In particular, the conditions of cratering and meteorite fall on the planetary surface are obtained. The results are presented in a simple analytical form. They quite match to the real events considered in the paper. Recommendations are given on further investigations into the important problem of interaction of cosmic bodies with planetary atmospheres.

The signatures of planets hosted by M dwarfs are more readily detected with transit photometry and radial velocity methods than those of planets around larger stars. Recently, transit photometry was used to discover seven planets orbiting the late-M dwarf TRAPPIST-1. Three of TRAPPIST-1's planets fall in the Habitable Zone, a region where liquid water could exist on the planetary surface given appropriate planetary conditions. We aim to investigate the habitability of the TRAPPIST-1 planets by studying the star’s activity and its effect on the planets. We analyze previously published space- and ground-based light curves and show the photometrically determined rotation period of TRAPPIST-1 appears to vary over time due to complicated, evolving surface activity. The dramatic changes of the surface of TRAPPIST-1 suggest that rotation periods determined photometrically may not be reliable for this and similarly active stars. While the activity of the star is low, we use the premise of the “cosmic shoreline” to provide evidence that the TRAPPIST-1 environment has potentially led to the erosion of possible planetary atmospheres by extreme ultraviolet stellar emission.

We present a study of the effects of ultraviolet (UV) emission from active galactic nuclei (AGN) on the atmospheric composition of planets and potential impact on life. It is expected that all supermassive black holes, which reside at galactic centers, have gone through periods of high AGN activity in order to reach their current masses. We examine potential damaging effects on lifeforms on planets with different atmosphere types and receiving different levels of AGN flux, using data on the sensitivity of various species’ cells to UV radiation to determine when radiation becomes “dangerous.” We also consider potential chemical changes to planetary atmospheres as a result of UV radiation from AGN, using the Platform for Atmosphere, Land, Earth, and Ocean photochemical model. We find that the presence of sufficient initial oxygen (surface mixing ratio ≥10−3 mol mol−1) in the planet’s atmosphere allows a thicker ozone layer to form in response to AGN radiation, which reduces the level of dangerous UV radiation incident on the planetary surface from what it was in absence of an AGN. We estimate the fraction of solar systems in galaxies that would be affected by substantial AGN UV radiation, and find that the impact is most pronounced in compact galaxies such as “red nugget relics,” as compared to typical present-day ellipticals and spirals (using M87 and the Milky Way as examples).

The diverse planetary environments in the solar system react in somewhat different ways to the encompassing influence of the Sun. These different interactions define the electrostatic phenomena that take place on and near planetary surfaces. The desire to understand the electrostatic environments of planetary surfaces goes beyond scientific inquiry. These environments have enormous implications for both human and robotic exploration of the solar system. This book describes in some detail what is known about the electrostatic environment of the solar system from early and current experiments on Earth as well as what is being learned from the instrumentation on the space exploration missions (NASA, European Space Agency, and the Japanese Space Agency) of the last few decades. It begins with a brief review of the basic principles of electrostatics.

Aggregation of sub-mm particles in strong electric fields under microgravity conditions

The distribution of instellation at the top of a planet's atmosphere or surface is usually calculated using the inverse-square law of radiation. This is based on the assumption that the host star is far enough to be considered a point-sized Lambertian source. This assumption, which works well for the solar system planets and most exoplanets, must be revised for close-in exoplanets. The objective of this work is to derive accurate instellation patterns for close-in exoplanets, for which the effects of the spherical shape of the star must be taken into account. First an analytical formula of the insolation as a function of latitude was derived, taking the star and the planet as 3-D bodies, and incorporating the limb darkening effects of the star. Then numerical techniques were used to compute the distribution of the insolation on close-in planets as a function of latitude for a wide range of stellar and planetary properties.There are significant deviations in instellation values and their distribution on close-in exoplanets, due in similar proportions to the physical size of the star and stellar limb-darkening effects. The insolation at the susbtellar point is always higher -- by as much as 21% for known exoplanets -- than the standard calculation. The substellar longitude of the terminator can significantly extend on the nightside, from 90 degrees up to 110 degrees for known exoplanets.

The hypothesis that CI meteorites have an origin on Mars is presented along with supporting data and implications. A Martian origin for the CI will support Martian biogenesis and effect assessments of Martian histories, suggesting Mars and Earth evolved in parallel in both biologic and geologic realms for a long period. The CI containing a Martian pattern of oxygen isotopes and mineralogy indicative of deposition by liquid water. The CI contain no evidence of hypervelocity impact, but contain space-exposed olivine grains and are thus regolith material, indicating their formation under a planetary atmosphere. They contain organic matter similar to that found in Martian meteorites, ALH84001 and EETA79001. A scenario of formation of CI meteorites as being water altered late planetary accretion material is proposed. The 4.5 Gyr age of the CI, matching ALH84001, and their high concentration of organic matter, including possible fossil bacteria, strongly supports the hypothesis of early Martian biogenesis. With CI plus ALH84001 being old, and the SNCs being young, the Martian crustal age dichotomy is now well reflected in Martian meteorite ages. This suggests Mars has a strongly bimodal pattern of crustal ages, either very old or very young with liquid water moving on the planets surface until late in the planets history.

This paper begins with a presentation of some important aspects of the science behind global warming. Following that, I argue that attempts to address global warming and climate change as problems facing humanity ought not to center around economic understandings of the problem or it solutions. Moreover, I argue that (environmental) pragmatism is especially vulnerable to this sort of misappropriation in seeking solutions to climate change, and that environmental pragmatists ought to make a conscious effort to avoid potential mischaracterizations of pragmatism by providing a clearer sense of the boundaries that delimit its approach to climate change, or any other environmental crisis.Public discourse concerning the rising average surface temperature of our planet is not far to seek at present. There is almost daily mention of the phenomena in print, radio and television news media; and no shortage of special reports by various stations and channels, Discovery and PBS: Frontline1 are two that come to mind), special issues of periodicals, or documentaries (think former VicePresident Gore) all addressing some aspect of the myriad concerns over the continued burning of fossil fuels and its effect on the climate. In what follows, I first provide a lay account of the science of global warming; one that I hope will interest readers not already preoccupied with the subject, as well as further inform those who are. Following that I argue that attempts to address global warming and climate change as problems facing humanity ought not to center around economic understandings of the problem or it solutions, and that pragmatism especially ought to resist such an approach.1. The Balance of EnergyEarth receives energy from the Sun in the form of light (much of which is not within the visible range of human beings). Various frequencies of light carry energy across the 150 million kilometer wide vacuum that separates the Sun from the Earth.3 The heat provided by the sun is crucial to making our planet inhabitable. Theoretically, the Earth should overtime radiate or reflect back into space the same amount of energy that it receives from the Sun - barring temporary or regional imbalances.4 I will refer to this throughout this essay as the Earth's energy balance or energy budget.What this means is that if we consider the total amount of solar energy that reaches the Earth that same amount of energy must be returned to space by the Earth. All solar energy comes at the Earth from one direction, but energy is radiated from the Earth in all directions. Light that is reflected by the Earth's atmosphere back into space never reaches the planet's surface. The total energy release from the earth can be divided into two broad categories: heat radiated and light reflected. The first category - the heat radiated from the Earth - accounts for approximately seventy percent - roughly fifty eight percent by clouds and the atmosphere and twelve percent by near surface emissions - of the solar energy that the Earth receives from the Sun. The other category - light reflected - accounts for the solar energy that is reflected back into space - approximately twenty three percent by clouds and atmosphere and seven percent by the surface of the Earth.5 The total amount of visible light reflected - as opposed to radiated - by a body is called its albedo^ and in climatology is sometimes expressed as a percentage of the total incoming light. Earth's albedo is roughly .30; that is, thirty percent of the visible light from the Sun is reflected back into space before it enters the planet's atmosphere.2. The (Anthropogenic) Greenhouse EffectGases present in the Earth's atmosphere are classified as greenhouse or nongreenhouse gases based on whether their molecules are reactive to infrared (IR) light. If a molecule has three or more atoms, it is infrared active. Gases are not good blackbodies - objects that absorb and radiate all frequencies of light - because they are very selective about the frequencies of IR light they will interact with. …

Observations of Mars from Earth between 1965 and 1969

The resistance of the lichen Circinaria gyrosa (nom. provis.) towards simulated Mars conditions—a model test for the survival capacity of an eukaryotic extremophile

We use 3D hydrodynamics simulations followed by synthetic line profile calculations to examine the effect increasing the strength of the stellar wind has on observed Ly α transits of a hot Jupiter (HJ) and a warm Neptune (WN). We find that increasing the stellar wind mass-loss rate from 0 (no wind) to 100 times the solar mass-loss rate value causes reduced atmospheric escape in both planets (a reduction of 65 per cent and 40 per cent for the HJ and WN, respectively, compared to the ‘no wind’ case). For weaker stellar winds (lower ram pressure), the reduction in planetary escape rate is very small. However, as the stellar wind becomes stronger, the interaction happens deeper in the planetary atmosphere, and, once this interaction occurs below the sonic surface of the planetary outflow, further reduction in evaporation rates is seen. We classify these regimes in terms of the geometry of the planetary sonic surface. ‘Closed’ refers to scenarios where the sonic surface is undisturbed, while ‘open’ refers to those where the surface is disrupted. We find that the change in stellar wind strength affects the Ly α transit in a non-linear way (note that here we do not include charge-exchange processes). Although little change is seen in planetary escape rates (≃ 5.5 × 1011 g s−1) in the closed to partially open regimes, the Ly α absorption (sum of the blue [−300, −40 km s−1] and red [40, 300 km s−1] wings) changes from 21 to 6 per cent as the stellar wind mass-loss rate is increased in the HJ set of simulations. For the WN simulations, escape rates of ≃ 6.5 × 1010 g s−1 can cause transit absorptions that vary from 8.8 to 3.7 per cent, depending on the stellar wind strength. We conclude that the same atmospheric escape rate can produce a range of absorptions depending on the stellar wind and that neglecting this in the interpretation of Ly α transits can lead to underestimation of planetary escape rates.

Tissint (Morocco) is the fifth martian meteorite collected after it was witnessed falling to Earth. Our integrated mineralogical, petrological, and geochemical study shows that it is a depleted picritic shergottite similar to EETA79001A. Highly magnesian olivine and abundant glass containing martian atmosphere are present in Tissint. Refractory trace element, sulfur, and fluorine data for the matrix and glass veins in the meteorite indicate the presence of a martian surface component. Thus, the influence of in situ martian weathering can be unambiguously distinguished from terrestrial contamination in this meteorite. Martian weathering features in Tissint are compatible with the results of spacecraft observations of Mars. Tissint has a cosmic-ray exposure age of 0.7 ± 0.3 million years, consistent with those of many other shergottites, notably EETA79001, suggesting that they were ejected from Mars during the same event.

Understanding whether M dwarf stars may host habitable planets with Earth-like atmospheres and biospheres is a major goal in exoplanet research. If such planets exist, the question remains as to whether they could be identified via spectral signatures of biomarkers. Such planets may be exposed to extreme intensities of cosmic rays that could perturb their atmospheric photochemistry. Here, we consider stellar activity of M dwarfs ranging from quiet up to strong flaring conditions and investigate one particular effect upon biomarkers, namely, the ability of secondary electrons caused by stellar cosmic rays to break up atmospheric molecular nitrogen (N(2)), which leads to production of nitrogen oxides (NO(x)) in the planetary atmosphere, hence affecting biomarkers such as ozone (O(3)). We apply a stationary model, that is, without a time dependence; hence we are calculating the limiting case where the atmospheric chemistry response time of the biomarkers is assumed to be slow and remains constant compared with rapid forcing by the impinging stellar flares. This point should be further explored in future work with time-dependent models. We estimate the NO(x) production using an air shower approach and evaluate the implications using a climate-chemical model of the planetary atmosphere. O(3) formation proceeds via the reaction O+O(2)+M→O(3)+M. At high NO(x) abundances, the O atoms arise mainly from NO(2) photolysis, whereas on Earth this occurs via the photolysis of molecular oxygen (O(2)). For the flaring case, O(3) is mainly destroyed via direct titration, NO+O(3)→NO(2)+O(2), and not via the familiar catalytic cycle photochemistry, which occurs on Earth. For scenarios with low O(3), Rayleigh scattering by the main atmospheric gases (O(2), N(2), and CO(2)) became more important for shielding the planetary surface from UV radiation. A major result of this work is that the biomarker O(3) survived all the stellar-activity scenarios considered except for the strong case, whereas the biomarker nitrous oxide (N(2)O) could survive in the planetary atmosphere under all conditions of stellar activity considered here, which clearly has important implications for missions that aim to detect spectroscopic biomarkers.