The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report

The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument

The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report

The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument.Comment: Full report: 498 pages. Executive Summary: 14 pages. More information about HabEx can be found here: https://www.jpl.nasa.gov/habex

Priming Bean Seedlings to Boost Natural Plant Defenses Against Common Bacterial Wilt: Leaf Architecture, Leaf area, Foliage Water Content, and Plant Biomass Results (Part 3)

This greenhouse study evaluated the effects of two chemicals for priming kidney bean seedlings against bacterial wilt disease (Curtobacterium flaccumfaciens pv. Flaccumfaciens) (CFF). The premise of this study was that the oxidant properties of chlorine dioxide would mimic the signaling properties of radical oxygen species thereby initiating a cascade of molecular plant defenses. The factorial study included two levels for the foliar chlorine dioxide treatment, two levels for the bacterial wilt inoculation treatment, and two optional treatments. The biomass variables included oven dry total plant biomass, oven dry fruit biomass, and oven dry leaf biomass. Also, foliage and total plant water content data was collected, as well as total leaf area. Specific leaf area (SLA) was estimated from the leaf area and biomass data. The primers had equivalent leaf area, plant and fruit biomass as the water control for the CFF wilt inoculated plants. The EB 400 mg/l primer reduced SLA for the CFF inoculated plants. Both EB formulations increased aboveground water content in the CFF wilt inoculated plants. Multivariate tables revealed several significant correlations among leaf architecture, plant tissue water content, and biomass growth parameters for the EB primers and the water control treatment for the two CFF wilt treatments. Re-allocation of plant resources from plant growth to plant defenses due to chemical primers were estimated and discussed to determine the tradeoffs between plant yield and enhanced plant defenses. The three articles in this study show that chlorine dioxide primers can initiate a series of ROS and salicylic acid signals. This interplay of ROS signals and salicylic acid signals generated by the chlorine dioxide primers activates a long-term SAR response that protects plants against future pathogen attacks. In addition, interaction of the ROS and salicylic acid signals activates a suite of defense mechanisms that provide universal, multifaceted plant immunity that can be sustained across a crop season

Priming Bean Seedlings to Boost Natural Plant Defenses Against Common Bacterial Wilt: Salicylic Acid Responses to Chemical Primers (Part 1)

This greenhouse study evaluated the effects of two chemical inducers for priming kidney bean seedlings against a bacterial wilt disease. This study's central premise was that chlorine dioxide's oxidant properties would mimic the signaling properties of radical oxygen species, thereby initiating a cascade of molecular plant defenses, including the synthesis of salicylic acid (SA). This signaling agent then initiates a cascade of pre-defense activities to provide a more rapid and robust natural defense against pathogen attacks. This factorial study included two levels for a foliar chlorine dioxide treatment and two for a bacterial wilt inoculation treatment. The two plant response variables were free and conjugated salicylic acid levels sampled in leaf tissue over two collection dates. Half of the 96 plants were inoculated with a bacterial culture that causes common bean wilt disease. Leaf tissue was harvested 17 to 32 h and 960 h after the wilt inoculation to determine the temporal dynamics of SA due to chemical treatments. Also, PCR tests were used to verify wilt presence in the inoculated plants. Inoculation of the wilt disease did not affect free SA when leaf tissue was sampled from 17 to 32 h. after wilt inoculation. However, chlorine dioxide applied at 400 mg/l and sampled at 20 h after inoculation resulted in a 15-fold increase in free SA over the control. Also, chlorine dioxide applied at 400 mg/l with leaf tissue sampled at 26 h after inoculation resulted in a 33-fold increase in conjugate SA levels compared to the control plants. Leaf tissue sampled at 960 h after the inoculation showed no free SA differences among the chemical treatments. However, the inoculated plant had a 15.9-fold increase in free SA compared to the non-inoculated plants. The priming effect on kidney bean seedlings using a single chlorine dioxide foliage application temporarily increased free and conjugate SA. The free and conjugate SA levels for the non-inoculated plants returned to baseline levels when sampled at 960 h. These results indicate that primed plants elevate SA up to several weeks with a slow decline back to baseline levels. Stem injection of the bacterial wilt bypassed the immunity mechanisms present in leaves, which significantly increased the wilt injury levels. Stem injection negated much of the foliar defenses, which overshadowed the priming effects of the chemical treatments on plant immunity and foliar defenses. The second leaf sampling on newly formed leaves reveals elevated SA levels in the inoculated plants but not in the non-inoculated plants