The EChO Mission

by | Dec 21, 2011 | Current Events, Daily Paper Summaries

• Paper title: EChO: The Exoplanet Characterization Observatory (arXiv: 1112.2728)• Authors: G. Tinetti et al• First Author’s Affiliation: University College London, London, UK.• Journal: Accepted for Experimental AstronomyOverviewThis paper describes a proposed ESA M-class mission , the 1.5-meter Exoplanet Characterization Observatory (EChO).The idea behind EChO is simple: to provide a dedicated platform for exoplanet characterization, i.e. to figure out what’s in the atmospheres of planets around other stars. Missions like Kepler do a great job at finding extrasolar planets and at estimating their sizes. Most of these worlds can be massed as well, using techniques like radial velocities and transit timing variations. These are fantastic measurements that let us build up a broad picture of the exoplanetary population. However, as Figure 1 shows, mass and radius alone tell us almost nothing about what might be in a planet’s atmosphere, and what conditions on the surface (if it even has one) are like. Understanding atmospheric and surface composition is critical to a complete theory of the formation, evolution and dynamics of planets, as well as in determining whether or not they might be habitable. For example, Earth and Venus share similar masses and radii, but life as we know it would be hard-pressed to exist on the lead-melting surface of Venus!Spectroscopy allows us to break this degeneracy and directly characterize exoplanets. By looking for the spectral imprint of different substances, we can figure out the composition of the atmosphere as well as its temperature structure (if a feature is observed in absorption, then that substance is hotter deeper in the atmosphere; if in emission, then the opposite is true).EChO proposes...
Jupiter: Friend or Foe?

Jupiter: Friend or Foe?

by | Nov 16, 2011 | Daily Paper Summaries

Paper title: Jupiter: Friend or Foe IV: The Influence of Orbital Eccentricity and Inclination (arXiv:1111.3144) Authors: J. Horner, B. W. Jones  First Author’s Affiliation: University of New South Wales, Sydney, Australia MotivationThe hunt is on to find habitable exo-Earths, but what does “habitable” actually mean? The traditional definition of habitability focuses on the surface temperature of the planet: specifically, is it in the correct range to support liquid water? However, there are many other components to habitability. For example, if the star is too active and the planet too close to it, stellar activity and radiation may create a hostile environment for life to form. Another constraint on habitability comes from meteorite impacts: if the planet is hit by the equivalent of a Yucatan impactor (i.e. the one that killed the dinosaurs) every few millenia, it will be challenging for complex life to evolve there!In this paper, Horner and Jones focus on the impactor constraint for habitability. The existence of Jupiter is often cited as a factor in Earth’s habitability because the larger planet gravitationally shields Earth from most asteroid and cometary impacts. However, Jupiter is on a very sedate, low-eccentricity, low-inclination orbit, and the search for exoplanets has turned up gas giants with a wide range of inclinations and eccentricities. How would varying the eccentricity and inclination of Jupiter affect the impact rate on Earth? This is the question this paper asks. By understanding the influence of co-systemic giant planet eccentricity and inclination on the rate of impacts onto potentially habitable planets, it will be possible to more tightly focus the search for habitable exoplanets on systems that...
ExoMoons and ExoEarths

ExoMoons and ExoEarths

by | Oct 19, 2011 | Daily Paper Summaries

• Paper title: Modeling the Infrared Spectrum of the Earth-Moon System: Implications for the Detection and Characterization of Earthlike Extrasolar Planets and their Moonlike Companions (arXiv:1110.3744v1) • Authors: Tyler D. Robinson • First Author’s Affiliation: University of WashingtonIntroduction The holy grail of exoplanet scientists is the detection and characterization of a true Earth-analog, an “Earth-twin” orbiting another star. A number of great studies have been done towards this goal; see for example the EPOXI mission, which turned the sensors on Deep Impact back towards Earth to see what we could learn about its atmosphere from remote observation alone. Yet many of these studies consider the Earth in isolation. They ignore the fact that we have a very significant companion in the form of the Moon. Given how close the Earth and Moon orbit, it is unlikely that any exoplanet characterization mission we can envision will be able to resolve an Earth-Moon system analog (the Earth-Moon separation would be 5 milliarcseconds at just 5 parsecs). Therefore, any spectra we take of a terrestrial planet would likely include flux from unseen companions. Recent planet formation modelling suggests that impacts of the kind that formed the Moon may be common. What would be the effect of a lunar companion on measured atmospheric spectra, and how might we ascertain the existence of such a companion? This article explored these questions.MethodThis paper builds on previous work that looked for the effect of a lunar body on an Earth-analog in a bolometric (i.e. total luminosity) sense, which found that the orbiting body needed to be Mars-sized in order to be detectable through broadband photometry. In...

Journey to Mars

by | Mar 26, 2011 | Personal Experiences

This past February, I had the opportunity to travel to Mars – or just about as close as you can get on Earth. I was privileged to be a part of the all-student Crew 99 of the Mars Desert Research Station (MDRS), which did work on astrobiology, mission planning, and astronomy engineering.MDRS is an analog Mars facility in the Utah desert, built, owned, and operated by the Mars Society (purpose: “to explore and settle the planet Mars”). The objective of the facility is to simulate living and working on Mars, so we can encounter, overcome, and learn to manage as many problems as we can before actual landings and exploration commence. During the January-April field season, crews of 6 head to MDRS for 2-week rotations. In addition to the general Mars exploration objectives associated with MDRS, each crew also brings with it a slate of scientific research objectives, often related to astrobiology or exploration engineering.Our crew was built around our astrobiology experiment: project LAMBDA. LAMBDA was an extension of our summer 2010 group project as part of the NASA Ames Academy for Space Exploration. LAMBDA was inspired by a couple of papers (Abrevaya et al 2010, Miller and Oremland 2008) which explored a new way to detect life: microbial fuel cells (MFCs). The idea goes as follows: all known life metabolizes, and in particular metabolizes via redox biochemistry. Microbial fuel cells use these redox reactions to generate electricity. Redox reactions in the anode chamber generate free electrons. Electronegativity differences between the anode and cathode cause electrons to be taken up by the electrodes and flow from the anode to...