リボ核酸（RNA）の原始的な生成経路を明らかにする研究の一環として，ペプチドやアミノ酸熱重合物を触媒としてアデノシン5'-三リン酸（ATP）からオリゴアデニル酸（oligo(A)）が自発的に生成するかどうかを調べた．3種類のジペプチド，2種類のポリペプチド，および種々のアミノ酸熱重合物の共存下で表記の反応が進行するかどうかを分析的，速度論的に解析した．結果として，これらのペプチド類あるいはアミノ酸熱重合物の共存下ではATPからはoligo(A)は生成しなかった．また，いくつかのアミノ酸熱重合物はATPの加水分解反応を2倍以上促進した．この事実は，無秩序なアミノ酸熱重合物はATPからRNAが生成する反応の触媒とは原始地球環境下でもなりにくかったことを示している．その理由を考察するために，活性化ヌクレオチドとしてのヌクレオシド5'-三リン酸（NTP），ヌクレオシド5'-二リン酸（NDP），およびヌクレオシド5'-リン酸イミダゾリド（ImpN）の平衡論的および速度論的な性質の違いを比較し，重合反応の機構を考察した．以上の結果からは，NTPがRNAの原料モノマーとして利用されるためには高度な触媒作用が出現することが必要であったと推定される．また，RNAの生成様式を化学進化の過程に対応して3段階に分類し，ImpN，NTP，およびNDPの化学進化上の役割を推定してRNAおよびRNAポリメラーゼの化学進化のシナリオを描いた．

This special issue is based on a symposium Extraterrestrial Exploration Projects in Japan that was held in March, 2002 at the 27th annual conference of this society. In this symposium, three invited speakers introduced Extraterrestrial Exploration Projects in which they participate. Dr. Haruyama presented on the SELENE project toward the moon and future plans of moon development. Dr. Yano introduced the asteroid exploration and sample return mission called MUSES-C. In addition, he showed a future planning of the exploration of asteroids and planets. Dr. Tamura summarized the extra-solar planet detection programs and some subjects that should be focused in this field.

  More than 30 years ago, American astronauts arrived at the Moon and left their steps as first ones of human beings. At that time, we believed that everyone who wants would be able to go to the space without any problem in the 21st century. However, we can't visit even the Moon again, today. We, Japan, are preparing Moon explorations steadily. In this paper, we introduce the current status and future plans of the Moon explorations and discuss the role of the Moon explorations to studies of the origin and evolution of life.

  Origins of planetary systems and life are common goals among astronomers, biologists and planetary scientists. In the context of planetary exploration, astrobiology can be defined an interdisciplinary subject which answers fp, ne and fl parameters for the Drake-Sagan equation. The new concept of habitable zones also demands better understanding of primitive bodies of the solar system while “cosmic dust” is one of the key components that relates all the evolutionary stages (from the birth to the death) of the planetary systems and terrestrial life, for both the panspermina theory and the Urey-Miller paradigm. In particular, it is essential for us to properly conduct optical and spectroscopic observations of meteor showers such as the Leonid MAC and in-situ measurement and sample return missions to minor bodies such as MUSES-C, in order to connect between ground observation data of asteroids and comets and analytical data of cosmic dust and meteorite samples. For the latter, organic and prebiotic material analyses are important for both scientific outputs and space quarantine issues. Thus the primitive body exploration program should seek more collaboration with the astrobioloy community not only within the current program but also for new missions in the coming decade.

Since the discovery in 1995, extrasolar planets become a central topic in astronomy. In this review, briefly summarized are various methods for indirect detection of planets around nearby stars and related future projects. The difficulties associated with the direct detection, the next milestone in extrasolar planet studies, are discussed. A NASA’s approach for detecting and characterizing terrestrial extrasolar planets, TPF, is introduced. The Japanese working group for planet finding projects and its activities are also explained.