Mars exploration motivates the search for extraterrestrial life, the development of space technologies, and the design of human missions and habitations. Here, we seek new insights and pose unresolved questions relating to the natural history of Mars, habitability, robotic and human exploration, planetary protection, and the impacts on human society. Key observations and findings include:

1. – high escape rates of early Mars' atmosphere, including loss of water, impact present-day habitability;

2. – putative fossils on Mars will likely be ambiguous biomarkers for life;

3. – microbial contamination resulting from human habitation is unavoidable; and

4. – based on Mars' current planetary protection category, robotic payload(s) should characterize the local martian environment for any life-forms prior to human habitation.

Some of the outstanding questions are:

1. – which interpretation of the hemispheric dichotomy of the planet is correct;

2. – to what degree did deep-penetrating faults transport subsurface liquids to Mars' surface;

3. – in what abundance are carbonates formed by atmospheric processes;

4. – what properties of martian meteorites could be used to constrain their source locations;

5. – the origin(s) of organic macromolecules;

6. – was/is Mars inhabited;

7. – how can missions designed to uncover microbial activity in the subsurface eliminate potential false positives caused by microbial contaminants from Earth;

8. – how can we ensure that humans and microbes form a stable and benign biosphere; and

9. – should humans relate to putative extraterrestrial life from a biocentric viewpoint (preservation of all biology), or anthropocentric viewpoint of expanding habitation of space?

Studies of Mars' evolution can shed light on the habitability of extrasolar planets. In addition, Mars exploration can drive future policy developments and confirm (or put into question) the feasibility and/or extent of human habitability of space.

Field experiments were conducted to evaluate placement techniques for preemergence applications of pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] in grain sorghum [Sorghum bicolor (L.) Moench.]. The first technique consisted of row shields mounted behind the planter units. Shields maintained an untreated strip over the crop drill and allowed successful crop establishment with pendimethalin at 1.1 kg ai/ha, despite a simulated, intense rainfall of 3.8 cm within 24 h after planting. A second technique, which consisted of a special nozzle arrangement, was evaluated in no-till grain sorghum. The nozzle arrangement allowed a broadcast herbicide application but maintained an untreated strip over the crop drill. No stand reductions occurred using this technique at pendimethalin rates of 1.1 and 2.2 kg/ha. In a growth chamber experiment, preemergence applications of pendimethalin severely injured grain sorghum when the soil was wet at the time of emergence, but injury was reduced under hot, dry conditions.

HERB, a computer-based expert system for soybean weed management developed at North Carolina State University, was evaluated for managing weeds under Georgia conditions. The project was initiated in two phases: a) training Cooperative Extension county agents followed by evaluation in six Georgia counties and b) revision, licensing, and distribution across the state. Field evaluations indicated that HERB was not highly accurate for predicting final yield loss because of weed species senescence and environmental extremes later in the growing season. HERB generally provided a reasonable prediction for a positive economic return due to treatment approximately 60% of the time. Accuracy was directly dependent upon the accuracy of weed-free yield estimates and extremes in growing conditions. HERB should not be the sole source of weed management information but may be useful to producers and county agents where mixed or low populations of weeds exist. The program was distributed statewide in 1993 after revision, duplication, and training was completed.

Research was conducted from 1978 through 1980 at Headland, AL, to evaluate the use of herbicides, mechanical cultivation, and hand-hoeing as components of a total weed control system for peanuts (Arachis hypogaea L.). Herbicides or two cultivations alone failed to provide acceptable weed control, peanut yields, or net returns for the 3-yr period. However, adding two cultivations to the herbicide treatments produced acceptable weed control, peanut yields, and net returns for the 3-yr period. Average peanut yield for herbicide(s) plus two cultivations was 3200 kg/ha with an average net return of $260/ha. Two cultivations plus two hoeings without herbicide(s) produced good results with an average 3-yr yield of 3380 kg/ha and a net return of $280/ha. Herbicide(s) plus two cultivation treatments that had net returns equal to two cultivations plus two hoeing treatments were: dinoseb (2-sec-butyl-4,6-dinitrophenol) at 5.0 kg ai/ha applied at ground-cracking ($300/ha); dinoseb + alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] at 1.7 + 3.4 kg ai/ha applied at ground-cracking ($310/ha); and alachlor at 4.5 kg/ha applied preemergence ($320/ha). Treatments containing herbicide(s) plus two cultivations plus two hoeings did not substantially improve weed control, peanut yields, or net returns over herbicide(s) plus two cultivations.

For this presentation we would like to discuss some history of weeds and their control, the evolution of weed science, the development of herbicides and the changing dynamics of weed science research. As mentioned by previous speakers, weeds cause great loss to almost every crop production enterprise in the United States and around the world. Man has sought to control weeds by various methods including cultural practices, cultivation, hoeing, and with herbicides. Pioneer weed scientists were individuals trained in the areas of physiology, botany, and agronomy. They applied their knowledge and training to the understanding of growth, development, and control of weeds in the late 1800's and early 1900's.